I just ordered a SRT off MidwayUSA (the only good online parts store, CTD can suck one) for $49, its on backorder but they are expecting them on the 19th. I did a 2 day shipping so I will receive it quicker. I found a pretty simple "how to" online. I watched some videos but they are taking all the parts out of the frame, this how-to just handles the install, seems much quicker and more straight forward.
http://www.calguns.net/calgunforum/showthread.php?t=434741
Check it out, I'm EXCITED
Hard to beat Midway, Top gun is a good site for SIG stuff also. Of course a lot of their stuff is on back order also. http://www.topgunsupply.com/