IIRC, recommended mileage to change these is 121K. The 22Rx is an interference engine. If the TC lets go, you stand a chance of having the valves clang the pistons as part of your collateral damage, and you WILL be pulling the oil pan off. Sounds like you're going to be doing that anyway. The other real collateral damage you can potentially have is the TC cover getting worn thru from the chain slop. <img src="/forums/images/graemlins/shame.gif" alt="" /> <img src="/forums/images/graemlins/shame.gif" alt="" />

Check out the threads/tech article to see if you want to tackle this:

http://www.4x4wire.com/toyota/maintenance/timingchain/

Timing Chain Tech in Archive

If you can have him give these a read, go for it.