I have been to Harbin well over a dozen times, and mostly in the dead of winter. I would never ever want to be part of a tour group but it is nice to travel and experience things with others. YMMV. But there is really no need, especially if you have some Chinese language capability. I'll share my thoughts going there over an 11 year period through 2019.

To visit the Ice Festival at night the most you need is a taxi or didi who will take you, wait for you, and bring you back. Get their wechat so you can find them when you leave. You can try to arrange a taxi/didi on your own when you are ready to leave but what I saw was that it was a big hassle and they waited until they had 4 passengers going to roughly the same place. At night the Ice Festival really is spectacular but most people don't stay for even an hour. It is so bitterly cold. There are just a few heated indoor cafes and they ask each person to order at least a drink. Well worth it to warm up. If you like photography and it is your first visit you may end up spending over an hour. Phones stop working if you have them out too long so if you have some kind of pocket close to your body that can help. One of my employees put one of those handwarmers in his pocket wrapped in a wool glove and that worked well. I've had to put my phone inside my shirt against my chest more than once.

Try not to go the Ice Festival or Snow Sculpture Garden on your first day unless you are already acclimated to Arctic weather. Use the first 24 hours to get used to being outside. A good way to do that is to walk outside on the main shopping street with the Russian looking buildings and duck in a souvenir store when the cold becomes unbearable. It's now a pedestrian street and they also have a lot of snow sculptures along the street in the winter. Once I saw a very good sculpture of Marilyn Monroe with her skirt being blown up over a steam grate. A tour group came by and the leader complete with loud megaphone explained that all these sculptures were done by local high school students including this one of a beautiful young woman. And don't touch the sculpture anywhere! At the end of the street there was a sign explaining that the sculptures that year were done by invited international snow sculptors. I think that gives you an idea of the quality of information you may get on a local tour.

When you reach the Songhuajiang you can get out on it and walk, looking down 5 meters deep of frozen freshwater. They use it for additional car parking after it freezes.

There are a few Russian type restaurants, Hua Mei is OK and the interior is fairly authentic Russian, at least the dining room where we ate. It's on the main street with the other Russian type businesses. After a lengthy explanation of their special soup what we got was just a decent borscht. The dumpling restaurants we went to were really, really good. Especially Xi Jia De and there are others, too. You can ask your hotel for a reasonable place with great dumplings, these won't be on the main street.

Saint Sophia's cathedral is worth walking around both day and night. Very different looks. You can pay to go inside but it was stripped bare during the Cultural revolution and is now a museum. Orthodox cathedrals typically feature outstanding interior paintings but these were not restored. If you are only there once you can consider if you want to go in.

You need thermal underwear, easy to get at Uniqlo anywhere in northern China. I once went with an overweight Austrian who insisted he is used to the cold and did not need it. He regretted it. Forget what you look like, put as much moisturizer on your face that it can absorb, that will make a big difference how long you can stay out. And a ski mask or at the very least a good scarf which you will end up fashioning into a ski mask of sorts. (That's me)

At night it was -25 to -32 C. if you have not experienced that be sure to prepare. Can't emphasize it enough.

Do the Snow Sculpture Garden during the day, it does not look like much at night. Be prepared for a lot of walking even though on the map it looks like it is adjacent to the downtown area. There were no places to get warm the several times I went. Then at night head out to the Ice Festival.

I have been to Unit 731 which was more disturbing than any visit to a German concentration camp in Europe. It's far, we hired a taxi for the half day, and while I learned a lot it left me with more questions which I researched later. It's sobering to see how experiments were conducted on how long frostbite victims could survive and the attempts made at weaponization of diseases, the beginnings of biological warfare. While Harbin was essentially a Russian city before WWII, you'll learn why there was no European population left in Harbin after WWII. The commentary is highly politicized, just know that before going in. They even manage to through in a few digs against the Americans. And this place would not be for everyone, especially little children.

The Harbin Siberian Tiger Park looks to be open, went once and will never go again. I don't want to delve into OMNI territory but why there are commercial zoos where you buy a live chicken or even a donkey and watch it being killed and eaten by lions and tigers is beyond me. You tour the park in a bus with the top ripped off and caged over to protect the passengers. No heating, of course. I seemed to be the only one who saw any absurdity, not to mention lack of humanity, in caged humans being driven through an open zoo with a primary attraction of watching lions and tigers eat live domesticated animals thrown at them. The Siberian tigers are beautiful animals. But it gave me a lot to think about, none related to lions, tigers, or the infertile male ligers they crossbreed there.

Definitely choose a hotel with a decent location downtown. The local people are really nice, I always enjoyed dinner in a local restaurant there.

Sorry for the lack of organization, feel free to ask questions if you have any. If you really want to join a local tour I can make some enquiries Harbin is a city with a fascinating history, you will find it interesting and stimulating. And the Ice Festival is world class.