I agree that you needn't find a luxury tour company to ask them do every thing for you!
but I think as a foreighner travel in China, you don't know China at all, especially you can't speak local language,If you are not a backpacker, you acctually need a legal China travel agency to help you rent a car and sent an english tour guide for you(good historical and cultural knowlege)! they can make your tour convenient and safe on the other side.

If you take the taxi, it is ok, but I'm afraid a few of them will get higher price from you, you know evey country has this kind of person! sometimes, in rush-hour, you should wait for a long time to take a taxi. and language...is another problem.
Don't ask the hotel help you rent car and find tour guide, first, it is ilegal, They even do not have insurance and certification. second, the price will be much higher.
these are all personal suggestions, if you need I am very pleasure to give you some suggestions for your China tours!

have a good trip!