Bicycle Mechanics - knackered pedal...

so i know next to nothing about bikes, and am trying to fix up my old MTB rather than fork out on a new one for some round town transportation, anyway, onto the question...

Well my left pedal arm wobbles back and forth (perpendicular to the direction of rotation) and i think ive rounded off the bit where it joins onto the chain/gear piece (sorry if thats too technical :rolleyes:)
what would be the easiest/cheapest way to fix this?

The pedal spindle is bent. Replacement is the only solution. Use a 15mm wrench to remove, as it sounds like you used a 9/16th.

nah the pedal spindle is fine, but it wobbles at the top where it joins to the gear bit

ive worked out it's the left hand crank.

do i just need to buy a new one or do i need a whole crankset

Are both your cranks wobbly?

If they are, then the problem is probably the bottom bracket. Depending on the type of bottom bracket you have, it could be overhauled and adjusted, or just replaced with a $15 cartridge bottom bracket.

The problem is that you need a few specialized tools to do this job... And the bottom bracket is the single part on the bike that requires the most force to install properly. The cranks also need to be attached to the bottom bracket with a lot of force.

well ive taken bits of it apart just now, and the metal of the left hand crank is warped, so i think i just need a new one. Is the right one attached to the gear bit? because i couldnt get that one off

You'll need a crank puller to remove the drive side (you would have needed one for the non-drive side if it wasn't already knackered). And the drive side (right side) is connected to the chainrings AKA gear bit.

so would i be able to take off the drive side arm and replace it or not? I'd like symmetrical pedals lol.
Also could you reccomend a site where i could get the part(s) i need?

Is your non drive side arm simply loose on the BB spindle?