I am new to Volvos and I'm trying to get an idea of where my M41 is leaking from. What I've noticed so far...

1. The only pools (one silver-dollar sized) on the garage floor appear to be coming from underneath the filler/drain holes.
2. U-Joint rear of the OD had transmission fluid on it, was slinging it up around the car.
3. The ratty rubber boot for the clutch fork is wet with fluid. My oil pan is also leaking but I'm pretty sure this was transmission fluid. (Smelled like it.)
4. The bottom of the OD was pretty wet, not sure if it's coming from the speedo cable or anything.

My question is where do I start? How easy is it to replace problem seals? Another thing...I drained/replaced the fluid (the car was level) and removed a little over a quart and replaced it with about the same amount. I was anticipating putting in another half-quart. Was this because the OD was not engaged when I parked the car?

As always, thank you. I feel annoying asking so many questions but I want to learn!