Yes sir you can!!
Please read:
http://www.toyota-4runner.org/audio-electronics/63998-oem-navs-work-w-4r4.html
More info:
http://www.toyota-4runner.org/audio...nstall-2006-4runner-se-progress-findings.html
Summary: You can plug in just about anything so long as you make sure you get the right one. If have JBL, then refer to the first post. If you don't, again, refer to the first post I made. It will show you which NAVs are the ones for your truck (for example, E7005, E7009, etc). Also, because your rig didn't come with the NAV, you WILL have to splice into your VSS, Back up signal wire, and Parking brake signal wire. All info is in those 2 threads. You may have to get a wire plug (one of the eBay vender should sell it to you if they have it, it's a 25 pin (i think, I can't remember) plug. Otherwise, it's plug and play! If not, no biggie, you just won't have the Bluetooth/Rear Camera working. Also, don't forget you will need a GPS antenna, preferably from Toyota. Ebay venders usually have them (sometimes they sell it with the unit). There all some floating around on ebay, you have to check periodically for a good deal. I got mine for $700. Dealer cost: $4k+. I saw one on ebay the other day for $1500. Some on the forum will say screw it, get an aftermarket for that price.................. whatever, sorry, I'm rambling..........
Happy TurkeyDay............