new gmt800 owner, please help me sort some stuff out

[Stephen717]

Update, the truck runs, it's legal, I've been driving it to work, it needs tires, a clock spring for the steering wheel, and the plastic trim that covers the column. I also got a new high note horn for it since the old one didn't work anymore. The washer reservoir is replaced with a newer one someone replaced before their truck got wrecked (same one I got the horns off of), and I found a passenger door tweeter. I've ordered the ignition and door lock cylinders with matching keys so I can lock the truck, also ordered a new driver's door handle. The problems I'm currently running in to are that the passenger door won't unlock with the power locks, you have to push it back to the lock position and manually unlock it to open the passenger door, it also keeps promoting me to service the 4wd and I'm not sure how to do that since it's push button and all the units I ever dealt with had the shift selector on the floor, and the trans lever will shift through all the gears fine but when I put it in park and turn the truck off I can freely shift the transmission where any other vehicle I get into the trans shifter stays locked in park until the vehicle is running. The only other thing I noticed is sometimes when the parking brake is engaged the truck won't start and idk if that's a factory feature or some other problem I have to figure out. If anyone has any insight on these trucks please let me know.

Thanks,
Stephen