What is the year, make, model of your current vehicle?
I would not throw money at an oil consumption problem, most modern cars that suffer from it the root cause is failed\poorly designed oil control rings around the pistons. Cars can run surprinsgly well even when burning large amounts of oil, until the catalytic converter and oxygen (o2) sensors in the exhaust system are destroyed, at which point I would donate (disclose issues of course!), I did that with my 2000 corolla, from 70K-150K miles it was burning oil-- 1qt/100 miles near the end, and never broke down or left me stranded. I donated when the mpg dropped to about 15mpg, and CEL was indicating emissions systems failures.
The air conditioning, depending on climate is also rarely worth fixing.
The power windows can be caused by a variety of problems, but usually are either wiring (pinched wire in door panel), switch, or regulator related. I fixed these on my Saturn shortly before it was totaled. It was a matter of removing the door panel, and putting a multimeter at the 12V DC setting on the contacts on the motor. I verified it was getting +12V when the button was pressed one way, and -12V the other way, which told me the wiring\switch was functioning.
I ended up putting a bunch of white lithium grease on the channel, pulleys, and mechanisms. I loosened the bolts holding the regulator, and wiggled things around for a bit. The window then started working- it had simply frozen in place due to lack of lubrication. The cost of repairs was a special torx socket to remove door panel, and a can of spray grease, about $10 and 2 hours of time. If yours is more serious, it may require a regulator, these are expensive and a bit tricky to install.
Knowing the year, model, and make of your car will help you seek out others that have the same issues on specific forum sites and websites like carcomplaints.com and come up with the right fix.