As far as leather conditioning and restoration products go, I have had good luck in the past using Lexol. It is a two-step product consisting of a leather cleaner and a leather conditioner (you have to buy a spray bottle of each). It takes a while to do a whole interior, but it's definitely worth it.
For cleaning, you spray on some cleaner, lather a bit with a damp cloth, and then rinse with a clean, slightly more damp cloth. I find it's best to use a bucket of water and couple of microfiber towels and do one section of the seat at a time. The goal here is to really remove the dirt and open up the pores in the leather again.
After cleaning, you spray on the conditioner. This consists of oils and whatnot meant to bring back the softness and suppleness of the leather. Basically you spray it on one section at a time, work it into the leather a bit with a clean towel or rag, let it sit and penetrate for a bit, then wipe it down. The more you use, the better.
I have not used this on 4Runner leather, but in my Volvo it kept the seats looking brand new. I traded it in for the 4Runner at 140k miles and the salesman could not believe how good the interior looked--he said it looked like it had less than 20k on it! I'm sure there are other quality products out there too though.
