clearing xbox cache.....

so fallout 3 has started to lockup on me, and i've looked around a bit and it would seem that clearing my cache is the best thing to do, but apprently it will delete all my achievements for my games if im not online, im an offline gamer i dont have xbox live so this would be a real pain, i would like to know exactly what happens when i clear my cache. will it delete all my achevements, gamerscore and profile etc.....?

well i cleared the cache, it seems to have helped in the lag department and i havnt had any lockups yet, i just had to delete my fallout dlc and reinstall via the discs, and i plan to do that with my mass effect, borderlands, oblivion and what ever else dlc i have