Envoy error p0301 & p0014

[SlightlyAmused]

So this will be my first time posting here, I'm looking to sell my 02 envoy and need it to be back in great shape. Recently the check engine light has been coming on and flashing when I hit about 40mph to 60mph. It moves sluggish uphill, almost no acceleration at those points, and it runs extremely rough when I accelerate randomly. It is a 02 SLT with 125,000 miles.

So, after getting the codes checked (p0301 & p0014) and a bunch of research on this form and a few others I think I have the problem figured out. I am by now means a mechanic, hence my post.

I plan on changing the spark plugs and cleaning the throttle body. What I am wondering is if anyone here has any other advice on what I might be able to do in order to get this beast back up to par.

Thanks!