Probably just the seal on the tranny. These are not hard to replace but you will need some heavy equipment to do it.
No heavy equipment or special tools needed.
The amount of stuff you need to remove to do anything makes working on the older ones seem overwhelming. As long as you accept it's gonna suck you'll be fine.
None of it's really hard, just time consuming and covered in 40 years of crap (technical term). They packed a lot of stuff in a tiny space.