Do you mean re-amping (changing the tone of the track you have laid down like from a clean fender tweed to an over driven Boogie) or do you mean playing back two separate guitar parts that were recorded at a different time (overdubbing) ?

Both are possible with either however you will need a pod or something to re-amp with the tascam. Re-amping is not such a good idea with an analogue recorder as with every bounce you lose quality.

You might want to check this thread out:

http://www.guitartricks.com/forum/showthread.php?p=87702#post87702