Congratulations on your Christmas present. Santa was never that good to me so i had to get the truck on my own!
If you have it running and it has a muffler, you will be able to tell some things about the motor. You can see if it puts out blue smoke and also listen for bearing knocks. Sometimes it isn't necessary to rebuild the motor.
In general, on my truck, I tried out everything mechanical that I could, excluding the brakes. The brake lines had rotted off so there was nothing to test. I did put the rear up on jack stands and tried all the gears.
Good luck and have fun.
