Hello Richard!
Wow, it’s been over 13 years since the last reply on this thread. I just spent a long time reminiscing about the memories of when my 4Runner was new and the backup camera, wood steering wheel swap, and the iPod adapter I installed.
Since the last time I replied to this thread I’ve gotten married, bought a new house, and had a baby and expecting a second baby anytime now, and guess what... my ‘03 4Runner is still running strong with no issues whatsoever all that time! Back up camera still works like a champ, as does the iPod adapter, with the same Gen 1 iPod attached (which still has an HDD inside spinning!), and the wood steering wheel looking as good as the day I installed it.
To answer your question on how to access the amp, there’s link a few replies above this thread that has step by step instructions, which I’ve copied here:
How to Remove the Navigation ECU from a 2003 Toyota 4Runner
Good luck!