o2 sensor and camshaft position sensor are bad on my Nubira

[MrbLOB9000]

I have a Daewoo Nubira CDX Wagon 2002. it seems like my car's falling appart. I need a new right and left lower control arm (posted about that here), which made me need two new front tires as well. I also need o2 sensors and camshaft sensor. I went to an authorized Daewoo mechanic and they checked my camshaft sensor for the recall and it's not the right lot number but it is bad so I have to get it and replace it. So far the cheapest locally I can find the o2 sensors and camshaft sensors are from CarQuest. $85 and $145 for the two o2 sensors and then like $48 for the camshaft position sensor. The brand on the o2 sensors are Bosch. I found a place online that had the o2 sensors for like $35 and $100 for Walker brand. Anyone used either brand before? Are they crap or what?

The other thing is, I only have 30k miles on the car, It's a 2002, I bought it used in 2003 with about 5k miles on it. Up to this point the car has been fine, I haven't had to do anything but all of a sudden recently everything's going to crap. I don't want to spend a grand on it now and then have a bunch more problems in 6 months or a year, but I don't want to sell it and spend money I don't need too to replace it if spending this $1,000 will get me another 3+ years of trouble free car usage. The other thing is, parts are hard to find, so if I do have a problem in a few years, I may just be hosed and it's not fixable, and that would truely suck. Any thoughts on whether I should keep it or if I should fix it and sell it?

Edit: the walker sensors I found are here http://www.mccullochs.com/WalkerOxygenSensors.html

[43som]

I own a 97 model, and the only work it has had recently between 160-198 thou, is the control arms, brakes, rear bearings and fan belt and timing belt and the gear box service.
this would have cost me maybe 1500 all up. i think the car will go on for another 100thou or so.