Gosh! Most people sound distressed about an install, I too have a 4 runner and had to trim the dash bezel.No big deal.
Ironically, I had previously owned a pullout(which I trimmed the dash for),and replaced it with a detachable unit.When I did so, I had to replace the trimmed dash bezel,and subsequently threw it away,thinking I would never need it again.(Obviously I was wrong) Anything is possible, it just depends on how bad you want it!
I have installed several dozen stereos in odd places for myself and friends. For example: cutting out and removing heater vents and ducts, ashtrays,gloveboxes,modifying seat frames,kick panels, so on and so on. Like I say it just depends on how bad you want it, and how creative you can get.
I will say though, if you aren't confident in any install,seek a professional. Downside is.......it'll cost ya!

Mk2 #105 12g blue
Car install complete...waiting patiently...again(extra sled for boat)