Quick, probably dumb questions from a transmission novice

Thanks to everyone for the helpful comments. Fortunately, room to work shouldn't be an issue for me because I am in the middle of a complete mechanical overhaul of the car ('73 Valiant slant 6). The short block and trans are still in the car, but everything that would normally be in the way is currently not, and I can rotate the engine and trans to make room to try to remove and replace the seals from the top. After reading all of the replies, that will be my first move and I'll only drop the valve body if I have to. Thanks again. I always appreciate the willingness of this group to share the wisdom.