Remapping a keyboard

hi people. i was wondering if anyone knew anything about remapping the keyboard keys. i'm thinking about getting a keyboard, however the key layout isn't exactly what i'd like it to be. specifically, instead of going option-command-spacebar-command on the bottom row, it goes command-option-spacerbar-option. in other words, the space bar is straddled by two option keys instead of two command keys. is there a way to switch the option key code or signal with with the command key, by either some terminal trickery or program? that would be great. thanks.

yeah that would be just the thing if it would install. for some reason the installer won't let it install on 10.3.3, but only 10.3.1 or 10.3.2.