1993 gmc 1500, transmission fluid leaking from yoke,and universal joint.how hard can this be to repair myself....... thanks.

My son has a 92 Dodge Stealth with auto trans. The past couple of months, from time to time, it would not want to go into park. So I would go in one motion from drive - low- park and that would do. However, other times, the car would not start unless you jiggled the gear shift. Tonight, he gets home but can't get the car in park the way I mentioned above, neither could I. After some jiggling and force, I got it into park. It won't come out now. I'm thinking this is a linkage prob, but I wanted some input before I tow it to the shop so I don't get hosed. What does this problem sound like and how major is it?