I installed a F900 in my 05 tC last month. It's pretty easy provided you use a wiring harness. I bought my harness through Crutchfield. I don't remember the exact cost but it was +/- $10.00.
For tips on modifying the stock mounting bracket so the door will still close, check out
http://www.scionlife.com/forums/viewtop ... +placement
For info on locating your GPS antenna and, if applicable, Sat radio antenna, check out
http://www.scionlife.com/forums/viewtopic.php?t=173399
For info the wiring harness and mounting kit check out
Wiring Harness: http://www.crutchfield.com/p_120701761/ ... ml?tp=2977
Mounting Kit: http://www.crutchfield.com/S-3XCA1soRug ... ml?tp=3121
You'll have to cut off part of the mounting bracket (on both left and right sides) in order for it sit flush against the side of the Nav unit's body. I didn't see this step discussed anywhere on the Scionlife forum but if you check out the photos the on this guy's install, and compare them to the photos shown on the crutchfield website, you can see where he modified the bracket.
http://www.scionlife.com/forums/viewtopic.php?t=165675
The hardware bypassed described on this forum works and is easy to do.
Hope this helps,
Mark