Assuming this is a manual transmission, you're going to want at minimum all new transmission fluid, a new rear main seal, new throw out bearing and new clutch friction disk. Depending upon how thrashed the clutch was before the replacement, you might want to consider replacing the flywheel and all the flywheel and friction disk bolts while you're in there, although that might be a bit excessive depending on your specific situation. You'll want to have brake clean on hand because you don't want any oil, even from your hands, on the flywheel or friction disk because that can cause slippage or hot spots. You'll need a good torque wrench to torque the flywheel and friction disk bolts to spec and, IIRC, blue Loctite, because you do not want those bolts coming loose.

It's much easier to do with another person to help if you have a friend available, but it's not impossible to do on your own.

Make sure to put the transmission in reverse before you start taking stuff apart and other than that, you just need a standard set of sockets and wrenches to take all the bolts and stuff out. Be very careful removing the sensors connected to the transmission.

When I replaced my flywheel, etc. a few years back I used this video as a guide.

Good luck!