904 Leaking Fluid

You will need a service manual. There are well over a dozen small bolts in the valve body but only some of them are long enough that they support the valve body. The other shorter ones are holding the 2 halves of the valve body together. If you take out all of the bolts you could have balls and springs to deal with. That means a simple seal R&R gets teribly complicted.
I dont do everything by the book though. Once I have the valve body removed I use a very small diameter long shank drill bit to make a pilot hole in the floor pan. Then I cover the trans with a towel, peel the carpet back, and push a 3/4 hole swa through the floor pan. This allows me to knock the new seal in from the top using a close diameter socket and extension. Body plug in the hole and it's there if/when I need it again.
If you try this, take your time, dont let drill chips fall in the trans or your eyes.