How difficult is it to replace a oil sending unit in a 1999 cadillac deville concours?

I am looking at a 1999 cadillac but they say the oil sending unit needs to be replaced and a engine reseal. how difficult would this be to do myself, or how much should I expect to be charged for this.|||the sending unit is,nt hard to replace. all you do is pull the wire off, screw the old 1 out and screw the new 1 in and put the wire back on. a engine seal? now that,s a different story and depends if it,s the front seal or back seal.|||The hardest thing on the oil sending unit will be finding it and getting to it. Generally there is just a wire that plugs on to it. Just un plug the wire and unscrew the unit. The engine reseal means new gaskets. Best to take it to a shop or maybe just walk away from it.|||the sensor simply screws in. the reseal is a large task. i dont know if i would buy it.