Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
You will want to just make sure that it's not oil that is getting on the engine and then burning off before you can see a leak.
However, the transaxle separator gasket, (and seal) are internal with the unit. Most times you will want to do a complete resealing of the transaxle while it is out. A good trans shop will probably want to charge more than what they should though.
Anyway, here are the labor times along with the prices of the parts, the entire seal kit is only $158, prices my vary. The labor should be, (at the most) about 7 hours or less.
I would figure at an average of $65 per hour anywhere from $600 to $800 depending on where you take it.
Auto Mechanic
ASE master, 30+ years. All makes and models. Trouble shooter, shop forman, service manager