if you follow all of the guides and steps to the letter, it greatly reduces the risk of bricking. there is always a chance of bricking though, you just have to take the plunge when youre ready.
i was extremely scared to do it myself, especially since i spent so much on this phone, until i said i gotta try it one day and after reading the unlocker thread, my tp was unlocked within 10 min with zero issues.
http://forum.ppcgeeks.com/showthread.php?t=42503
just follow here and good luck!!!