just did both mine a few weeks ago, the part is called an axle shaft seal, you can find it for about $10, I purchased mine at oreilly auto's.
As per replacing them, how mechanically savy are you? If not much (like myself) grab a chiltons manual and it will tell you everything, i can't stress this point enough!
get a balljoint separator!
have a 5lb hammer
have a 1/2" torque wrench with appropriate socket sizes for ball joints, and a 35mm axle socket
on the passenger side seal remove the lower shock bolt to lift the shock out of the way to make room to properly seat the cv joint on the axle shaft splines.
make sure you have two days to do this if your like me lol
2001 2dr. 4x4 LS - 235 75R15 Goodyear Wrangler silent armors, drop in K&N air filter, bedlined rocker panels/trim/bumpers, POR-15 underbody/frame, painted rear window trim.
JB Weld fixes everything... oh yes everything and anything...