It is unlikely, but possible, that it's your lower balljoint assembly. Put one hand on the balljoint as you rock it back and forth to make sure there's no play. You should also be able to reach behind the wheel and feel the bearing hub rock back and forth. It would really suck to change the wheel bearing just to turn around and have to essentially repeat the job to replace a balljoint. I very much suggest figuring out exactly what it is with 100% confidence before going further.
From what I can tell, yours won't require you to disassemble the knuckle, which makes the job quite a bit easier. It looks like you can can remove the axle nut, then access the bearing carrier bolts from the back. I've changed two sets of these types, and both times the bolts holding the bearing on were beyond tight. One I got loose with pb blaster and a BFW, the other required a torch to break the loctite.
This video is entertaining but a little painful, of an 02 park avenue.
https://www.youtube.com/watch?v=TMB2pJTydpA
This video is generic GM fwd, but easier to follow:
https://www.youtube.com/watch?v=eB9mrc4K0-c
The job can range from easy 1-2 hours per side up to one of those bearing bolts not coming loose and you fighting with it all damn day long.
Roommate/wife/friend's brother can be a gamble. It's a very straightforward job, but those bearing bolts need to be torqued TIGHT and you need to be careful with the cv axle when you slide it out. It is possible to screw it up. If changing brakes is a 3 on a scale of 1-10 I'd say this is a 5. A competent shop should be able to do it with no problem. If you do it, you will need to figure out the axle nut size and buy a socket unless you have a good set of tools.
If you plan on keeping this car you really should go ahead and replace both at the same time, especially if it's high mileage. They likely were pulled off the same shelf and have seen a similar life.
I wouldn't skimp on a bearing. Timken, moog, or OE acdelco. I would not do a POS autozone/advance house brand $40 part. This is one of those parts (like tires, brakes, suspension) where you life can depend on the part. Skimp on spark plugs, oil, or air filters if you want.
How long can you go on a failing bearing... It could fail in the next mile, it could go 1000's of miles. It's pretty rare to see them with play, usually they make a roaring noise and get stiff. So I wouldn't wait very long. One test is after a highway drive feel the wheel and see if it's noticeably hotter than the other side. A badly failed, nearly seized bearing will get very hot and should not be driven on.