Oil Pressure Sending Unit..How hard to replace?

I have a 97 4 cyl Grand Am. The oil sending unit is leaking oil. I want to know how hard it is to replace? I looked at it and it doesn't seem too difficult, but what I don't know is do i have to drain the oil before working on it? or can I just take it out and replace? How do I do this? Any help? This... show more I have a 97 4 cyl Grand Am. The oil sending unit is leaking oil. I want to know how hard it is to replace? I looked at it and it doesn't seem too difficult, but what I don't know is do i have to drain the oil before working on it? or can I just take it out and replace? How do I do this? Any help? This piece is right on top of the engine in easy reach...small and black. It has one of those metal rings that you tighten with a screwdriver and maybe have to have a wrench for the other side? Please help if this makes any sense.
Update: I just called the mechanic I usually go to and if I bring in the part, which is only $12.00 and IF it's as easy as it looks he says then he will charge me $40!!! That's ridiculous! He said it will probably take 30 minutes..I highly doubt that. Can anyone tell me how to change it myself? I don't mind... show more I just called the mechanic I usually go to and if I bring in the part, which is only $12.00 and IF it's as easy as it looks he says then he will charge me $40!!! That's ridiculous! He said it will probably take 30 minutes..I highly doubt that. Can anyone tell me how to change it myself? I don't mind getting my hands dirty.
Update 2: Jamie..it doesn't look hard to get to, it's right on top of the engine right next to where you put the spark plugs in. Right next to the big metal thing that says twin cam blah blah blah.
Update 3: I assume the engine should be cold? I mean for the more obvious reason that I don't want to get burned. I have done other work on my car, but had instructions over the phone from the guy who replaced my transmission, but he was nice and saved me $250! It was a fairly easy fix, but a tight squeeze for my arm.
Update 4: Converse: What is cross thread? Are you saying don't screw it in too tight?
Update 5: Dave..I do love my coffee, may take me a while! Like I said, I have done work on my car b4, changed the sparkplugs and ignition coil last week, noticed the fresh oil around this unit and some drips on the ground, so I figured I'd replace it to see if that's what's on the ground or something else.
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