An auto body shop seems like a good match for this job. Dealer or RV shop too. Which car did you settle on?
Look at the websites for Demco, Blue Ox, Roadmaster, and you'll see install instructions, a "difficulty index" and photos of completed installations. These can help you choose. Most tow bars can adapt to most base plates.
I've installed a half dozen base plates for self and friends. Once I got started, it was a little easier than the instructions would suggest. They are step-by-step to the extreme, so it reads like more work than it might actually be.
IF you need to drill the frame or unibody, you need quality drill bits. That stuff may be thin, but it's TOUGH.