I recently purchased a 2010 Giant Boulder SE for almost nothing, frame and headset in great shape. The rear axle was broken and even though i am on a tight budget, I did spring for a set of the 26" Vuelta wheels (rim brake )from Nashbar. I also bought a SRAM 7speed cassette and installed it on the new rear wheel with a spacer. I want to replace the crank/BB and will go back with another 3 sprocket crank. Anything I should know when looking for another crank since the bike now has a new rear wheel and a cassette? Possible alignment problems, maybe? I looked at the Shimano Acera crank on Jenson's site along with a Shimano UN-55 BB. I obviously still need to remove the existing crank and BB for sizing but want to know what to look for and if there are better options? Thanks.