30k mile checkup?

[Stratocaster5292]

I was pulling my 2000 Mustang GT out of the driveway and the shifter got stuck in reverse. After jiggling and massaging it for about 15 minutes it finally got to shifting again. My dad raised the question if I had gotten the 30k mile checkup yet, that maybe in the checkup they relubricate something in the transmission. Right now the car has 35k miles, and I bought it used when it had around 27k. I would check the owners manual, but the car didnt come with one. I couldn't find any information on it online so far and Im hoping someone could help me out with some info on the check up or if their car got stuck in reverse or some other gear and if they found out what the problem was. Thanks for any information. -Eric