Shift Selector Shaft Seal Remover tool

you can do it without the tool. not hard. let me find another post about it....
your link's not working and i can't find the post i was thinking about.
anyway, a service manual is a big help...

"MANUAL LEVER SHAFT SEAL
1)the seal can be replaced without removing the valve body by using a small screwdriver to pry the seal out of it's bore. be careful not to scratch the shaft or the seal bore.
2)drive in new seal with a 15/16 in socket and hammer"
if you do remove the valve body, you can drive it out from the bottom with a small punch.
either way, clean everything real good first. you can also drop the trans mount and lower the tail shaft a couple inches to get a little more room if needed but usually the exhaust is the what's in the way.

good luck