As Jim pointed out, you can find many tutorials for PID tuning by doing a Google search. There are also several good tips and suggestions for PID tuning here in our forum. The second half of this post on PID tuning also has some information that might help you get started.
To answer your second question, if you have a similar configuration and use the same motors as the 3pi, your PID constants might be similar; however, as Jim said, every robot is different.
-Brandon