I would consider things like the thermostat, hoses, the TPS, 02 sensor(s), water pump, etc a higher priority. Of course I'm assuming you're doing things like belts and tune-up stuff for sure.

The timing set can go much much farther than 200k without issue, but over time the chains get loose. If you have already replaced the other items I mentioned, and still have the time/money to do the timing set, since you're in this far I would do it.......at least then you can feel at ease when you're out away from home. Good luck and enjoy your trip! Sounds like quite an adventure. Take lots of pics for your blog and let us know how it goes. Tim

Update: Here's some important information regarding aftermarket timing sets: http://www.toyotavantech.com/forum/s...2491#post12491