theres nothing hard about getting to the up stream o2 at all. you need a o2 socket, then 12 inches worth of extensions and a ratchet or breaker bar, cause they get rusted in there. once it cracks free it comes right out. the socket cost 8 bucks at hf, change it your self. middle of the rear valve cover is a bracket with a plug on it, follow it down to the o2, its like right there in the rear manifold, cant miss it.

the down stream o2 likely will fight and not want to come out at all. shop with a torch when they do the cat might be best if you cant get it out.

napa has over head unlike most internet stores. stuff will cost more at the local parts store.

get delco o2's. why buy them later on when the denzos fail? wasted money, you get what you pay for. look on ebay for your o2, might find em cheaper. rockauto is usually pretty good on o2 prices as well.