sometimes it goes up sometimes it doesn't, and sometimes it goes partway, and then goes back down...

it is not a hard job... I have done them on other cars.

you pull the door car, see how it bolts in, unhook the glass, remove. as they say in the manuals, install is reverse of removal.

how much is the part online? I would wager 150-300?

That will do the same thing, otherwise, regulators are pretty common and you need to split the door to do it.

Somebody tried to save 12 cents on a plastic part and as a result they have a crap product. Purchasing people trying to save a some coin are killing this industry.

the window regulator isn't some kind of wear-and-tear part in which you'd be responsible for its failure. my airbag module or something went out 5k after warrantee was up, but they still did the work since i contended it wasn't my fault and they should stand by their product.

it's worth a shot, otherwise i think replacing it is a doable DIY, as others have said.