Transmission???

I have a 93 Park ave. the transmission will slip if I'm in Drive. but if I drive in 2 it gets me arround just fine. even shifts, But my question is will a tranny out of a 89 lesabre work in mine??? it has the 3800 like mine does.(my buddy just happens to have one with a blown motor) and if it will, is this something a backyard mechanic should tackle or pay a shop to do???? any advice would be appreciated????

As long as it is the same transmision, you should have in your park a 4T60-E