Older Giant Acapulco Left crank arm falling off

[dierad53]

Hello, I just got this bike. I paid 50 bucks which I thought was fair. It is a Giant Acapulco probably from the late 90s/early 2000s. The bike functioned well until today when I felt the pedal wobbling and the pedal fell off. So I was reading a few other forums and they said that the crank arm was most likely the problem. The nut also appears to be stripped. So my question is should I just go to a bike shop and get a new nut or should I just order a crank arm set off of ebay. Also if I order a crank arm off ebay which one should I get. I am looking to spend under 30 bucks for this since I am a broke college student who has a commutes 10 miles each day. Currently it has the stock crank arm.

[nfmisso]

no pictures => validity of answer is low.

I would purchase:
http://www.amazon.com/XLC-Head-Crank-Bolts-15mm/dp/B0043MQV2W/
http://www.amazon.com/Shimano-M131-Crankset-170mm-48/dp/B003ZMDJW6/
http://www.amazon.com/Shimano-BB-UN26-Square-Bracket-68x122-5-mm/dp/B0048MHCC0/

The new bolts because you said one was stripped; new BB for the same reason. Wobbly crank means that it is worn, and will always be wobbly.

You also need access to some bike tool, look for a co-op near you.