the reason shops quote a new pump, is that they tend to officially come as a whole pump/sender/housing drop-in unit on most gm's since the late 90's. however, the pump, and sender can be purchased separately, just pick a good brand. the thing is, though is that the sender can have a wear life between 100-160k, depending on how constant the fuel level is, and about 120k is the expected typical life of a pump, so replacing both at once just makes sense, really. one other thing to look at- the earlier style connector was a lesser design than the newer style, and you should check for an update. in all honesty, it takes me about an hour, or 2 in worse case, to pull the units out, just be real careful with the plastic lines, as you can bust those off easy if you just drop the tank down and tug on them. once you look at your float sensor plate, you will see a fan of lines, and a little tang that rides on them. a bad unit will have worn those down, likely at the top if you like to keep a full tank, and even can wear the tang down significantly. also, i have seen poor contacts on the jumper wires that go from the ext plug to the units themselves. this would be fuel contact sensitive. i suggest running the fuel as low as possible, if you haven't thought of it already. if you have some clean buckets and the proper fittings, you can even pump most of the fuel out via the fuel rail, or return line. once again, pick a higher quality pump, or sender, if you want it to last. i've seen many go out in a few months of use.