Thanks PharmSCRunner. BTW... you're referring to the PAC-SW, I'm assuming you mean the PAC-SWI-PS (PS stands for Pioneer Sony)... so I will refer to it as that but just making sure we both mean the PAC-SWI-PS. When I did mine I had the PAC TATO (to integrate my JBL system with the H/U) AND the PAC SW (to integrate the steering wheel controls). The best thing about that is the TATO comes with a wiring harness to use with your PAC SW that is preconfigured for our 4Runners. If you don't use (or don't need) the TATO then you will have to pre-wire the "generic harness" that comes with the PAC SW. Not a difficult thing, but I remember thinking... "whew, glad I don't have to do that".
Anyways, the SW comes with instructions that need to be followed. OR it comes with a website that narrows down the instructions depending on your car/head unit. Here are some of the sites so you can get a feel for what it is like.
http://www.pac-audio.com/swixprogramming/swixprogramming.asp
http://www.pac-audio.com/swixprogramming/showstepbystep.asp?InterfaceChecked=3&RadioGroupPioneer=1&mmSearch=Toyota&Submit2=Search+Vehicles&ID=65
If you're fairly new (which I am) then one thing you can use to tap into your fuses for power are these little mini fuses
http://www.amazon.com/Bussmann-BP-HHH-ATM-Add-A-Fuse/dp/B000GKEXK2 They plug into an existing fuse and has a wire to crimp your new power line. 2 fuses for the existing power line and the power line that you crimp. Shop around because you can find decent deals. They sell at autozone for about $6.99. Make sure you get good connections when you wire these up too. After my install, some things didn't work and I retraced my issues back to 2 of these MiniFuses that for some reason weren't giving power.
If I think of anything else, I'll let you know.
Hope that helps out a bit.