Ok I know timestretch is for changing the tempo without changing the pitch. But is there anyway to change the pitch of a sample with changing the tempo?
Actually it is an "option". There is a pitch shifter on the FX board.
Also, you could tune the sound (which shifts pitch but changes tempo), then timestretch to the proper tempo.
Stretching and shifting will always be better on a computer (any decent audio editor can do it), but for times you don't have access to one or want to just do something quick on the box, they are nice features to have around.