i have an 08' tc and want to change my cd player to a touch screen player...question is would it void any warranty? is it just plug and play? also thinking about doing the headrest...thanks.

No. Installation of an aftermarket radio alone will not immediately void your warranty, especially if installed professionally. Is it plug and play? Usually no. You have to buy the right adapter harness (e.g by Scosche) in order to install it to your stock harness.
Read this re. what voids your warranty http://www.scionlife.com/forums/viewtopic.php?t=55338

thanks man really appreciate it..