I inherited my wife's old Sequoia when we got her a new one (2008), so I have just begun making it my own.
First install: New Radio! That Stock JBL sounds good, but is seriously dated as far as functionality goes. It seems with Toyota that if you don't buy the top of the line, you don't get much.
I added a JVC KD-BT1 radio, with bluetooth built in and got the
ipod adapter. It allows for full control of
ipod through the radio. I used a special Scosche harness to allow me to use the JBL amp and speakers with the new HU.
Total install took about 2.5 hours. This includes soldering the Scosche harness to the radio harness, running the mic for bluetooth to just above the mirror, running the
ipod adapter to jsut below the front cup holders. The
ipod cable I routed up into the arm rest console.
The only wiring not taken care of by the Scosche was the antennae amp.
I used the blue/white wire off the radio and a vampire clip to the black/red wire on the stock harness. I was worried about power on the amp, but it's just a relay you're triggering, not supplying power.
Sound is great, especially with the JBL system intact. No real surprises there.
Bluetooth works great, it comes through the front speakers, the mic has good pickup, and you can sync several phones to the radio. Everytime the radio powers up it attempts to connect with whatever phones are paired to it, so you don't have to do anything to get hte phone working when you get in the car. You're suppossed to be able to upload your phone book to the radio, but I haven't tried that yet.
You can also use a device capable of bluetooth music streaming, so if you're MP3 device has that, you don't even need an adapter.
If not BT streaming, there is also a standard USB female plug that comes off hte radio and can be tucked away somewhere for memory sticks, Zune, etc.
Here's some links to the product I used. Everything was from Crutchfield, who deleivered great support. I expected the support as I paid more for the radio from them, but the special harnedd is 1/2 price if you buy a radio, so $$$ washed even.
Radio - JVC KD-BT1:
JVC KD-BT1 CD receiver at Crutchfield.com
Harness - Scosche Interface for Toyota JBL:
Scosche Interface for Toyota JBL Systems Allows you to install an aftermarket stereo and retain the JBL system in your 2003-up Toyota at Crutchfield.com
JVC
ipod Adapter:
JVC KS-PD100 iPod connection adapter for JVC stereos at Crutchfield.com
No other tools or wiring was pruchased.
Total cost for iequipment was around $400 delivered.