You have to lift the back of the engine about 4-5 inches to remove the transmission on my 94.
No,not a big job,only bolts to remove,no special tool if you just change the reverse plates.
Do a search here for transmission rebuilt.Good thread with a lot of pictures.
Low oil level would not cause to loose reverse.
Call Vince at Skidim.He is very knowledgeble and will tell you right away how to check if it is the reverse plates and how to check~replace everything.He s great to do business with!
Hurry,summer is short!
Edit:There should be a tag on the transmission with the maker and model numbers.
Or post a pix of it here,someone will bw able to ID it!