If i buy different sized wheels/tires (probably bigger) will I need to adjust my speedometer? or will someone else do it for me? and for what price?

If you use the proper plus sizing, speedo will not be an issue. Could be off 1-2mph, but nothing to have concern about. Plus sizing is basically increasing wheel size & shortening tire side wall.

To learn all about plus sizing & what affects it will have to your car - check out www.whalentire.com -www.tirerack.com