Chris, 1 question is what are you going to do with the car? Are you going to license and drive it, sell it or just keep it? I think a bill of sale is a good idea even if you don't have to actually show it. Notorized is better if you can do it. I would include
the year, make, model and color of the car and certainly the VIN number. Mom can sell it to you for $1.00 "and other valuable consideration". You have to put the purchase price on the title in CO when you sell a car and Michigan is most likely the same.
A good bill of sale might make the DMV lady or the sherrif who does the vin inspection a little less inquisitive. Envirotest does due VIN inspections but charges $25.00. I don't know if Weld is an emission test required county but if your going to sell
the car a "passed emmisions" certificate in hand is great for a Craigslist add. The passed test is good for 6 months.
Because the car is a gift I don't know how DMV handles the sales tax part if your going to license and drive it. They may charge you a use fee based on FMV or Kelly Blue Book. My guess is you don't get to drive it for free.