if you want to change out the 9853 for the 9855...like i did, you have to re-connect the alpine harness, they are not the same so you have to cut out the old one and try and make the same connections with the new one, it is a pain in the ass. I just hooked up my xmradio to it and it works...
shocks is a good idea, you may even need new one's after 127k...another thing to look at is the type of tires you have on the 4Runner. Tires can make a huge difference on the quality of the ride, check with your local tire shop and see what they say about the tires and make sure they are...