Quick, probably dumb questions from a transmission novice
you can get the seal out from the top with a small screwdriver or pick, but it's kind of a fiddly process and there's not a bunch of room for activities in there. but it's doable.
i find it easier to drop the pan, drop the valve body and pop the seal from underneath. throw a fresh filter and gasket on the pan while you're in there.
remember, there is *two* seals in there: one for the gear selector (gear lever) and the other for the throttle shaft (kickdown).
sometimes a groove gets worn into the shaft and you'll need the wider/taller seal which is #22072A