How much to have 700 R4 installed

[eighteenninetytwo]

I'm going to have to change out the tranny - it's pi$$ing fluid all over and rattles and grinds like nobody's business - to have the leaks stopped is several hours work and several hours work may as well be done installing a new one. This is NOT something that I could tackle myself at all. Question is how much should i be paying for it on top of the cost of the transmission itself? How long does it take? Another question is, currently vehicle has 4" lift. When I lower it back to stock, will there need to be further work on the transmission as the distance to the Rear axle will shorten very slightly?