Unless you have a good mechanical knowledge I suggest buying the LSD yourself to save markup, remove your tranny yourself to save labour costs, and get it installed in a shop to save hassles/money/time/damage to the rest of the transmission.
LSD's can go into any tranny that you can find one for basically, because it's not actually in the transmission itself... It's more like an anboard differential, mainly to save weight on the drivetrain from having driveshafts, and also a space issue in FWD's.
When you are working in a transmission, you need to know what you are doing with that transmission, there's alot of torque specs, clearences that .005 difference can cause you all hell... just my .02c though.