You could do what I've done and just service it yourself. Dealers literally sabotaged my car multiple times... Now I only go to a family run mechanic who happens to be very well off (not in it for the money) and only for part installs I couldn't do myself or didn't feel safe doing (water pump, exhaust headers, starter, etc.).
Don't get me wrong I knew nothing about mechanics work at first (never even changed the oil) but after picking up a very detailed service manual for my make and model and asking questions on car specific forums, I was well on my way to doing it all myself. The first year I changed; the oil 3 times, the wheels, front bumper, both differentials fluid, transfer case fluid, and replaced the battery. This year I ripped out the entire interior down to the metal to install some soundproofing and run my subwoofer wires as well as my Air Fuel ratio gauge cables from the extra "bungs" in my custom exhaust headers. I've recently replaced all my interior lights to red LED's as well, all things I had no clue how to do just 2 years ago.
For proof of oil changes, I keep my receipts and send oil samples to
Blackstone Laboratories (they even send you free containers to take oil samples). In 3-4 weeks they email or snail-mail you a detailed report containing details about your engine health as well as a full analysis of the oil and the metal content (also lets you know if you changed the oil to early or late). I also do this for my transmission, differential and transfer case fluids. I know this is a bit extreme but if I'm going to love the outside I also gotta love the inside.
Honestly, I feel like I should thank the dealerships for pushing me to do my own maintenance because I've learned so much invaluable information.
*Disclaimer mechanics work isn't for everyone and by no means is it easy, it's messy, hard, hands on work and you can get hurt or killed if you don't know what you're doing...