Bike 'jumps' when pedaling hard/uphill in high gears
I just bought a used Trek Mountain Track 800 for $120. I didn't get a good chance to test it beforehand, and I have very little experience doing anything with bikes other than replacing a punctured tire.
The problem is: whenever I am putting a lot of pressure on the pedals and pedaling hard -- ie on hard uphill climbs -- the pedals will 'jump.' It happens a lot when rear gears are in the 4 highest (4,5,6,7), and front is in the highest (3).
I looked at the chainring, and the teeth are a little bent. The "cogs" on the rear cassette look ok. I don't know very much about the chain itself other than it doesn't look bent :\.
Is it jumping because the teeth are bent on the chainring? Should I get a wrench/vice and try to straighten the teeth? Is there something wrong with the chain? Derailleur? I'm not sure how to fix much of anything, and I am just now learning all the parts of the bicycle, but I bought this bike partially for riding and partially to learn how to fix things (which I am not very good at). What can I do? Thanks.