Thank you for reminding me to post about my experiences.
In the end, subtracting all the travel time to and from, I had about 2.5 days in Scotland. To avoid a hectic schedule, I decided to stay and explore Edinburgh and save the Highlands outing for another time. The weather was a mix of rain, clouds and a bit of sun, so I wasn't sure how much I'd have enjoyed a train trip somewhere in the rain.
During my stay I walked around town a lot and visited Edinburgh Castle, the National Museum, and the Scottish Parliament building. The National Museum has a lot of exhibits and you can easily spend a day there. Calton Hill has some great views of the city and surrounding areas, as well as some interesting monuments. I also went to Leith to see the Royal Yacht Britannia. It was interesting, but fairly expensive for the self-guided tour. Since you can view most of the exterior from the upper floor of the mall building, check it out first and decide if you want to do the tour.
I found some good places for food & drink. Pep & Fodder has great coffee, pastries, and basic breakfast items. Urban Angel has some more extensive fare to get you going (I tried haggis there for the first time). I dined at The Dogs one night and would highly recommend it, but make sure to book ahead. The Holyrood 9A has great burgers and quite a nice craft beer selection. The Bow Bar and The Hanging Bat are quite good for that too. And I finished a couple of evenings tasting whiskies at The Albanach. Hope that helps, and let me know if you have more questions.