If you take your time..and check and recheck your work you should be fine. I haven't done a timing belt on a 4runner, but I have done many timing belts over the years. Last was my 98 Pathfinder.
If you have the time and patience, do it! I ordered my kit and had the dealer install - for all of the pulleys, belts, tensioner, fluid it was $562 including tax for the labor; add the parts and it was right at $1,000.00.
If you take your time..and check and recheck your work you should be fine. I haven't done a timing belt on a 4runner, but I have done many timing belts over the years. Last was my 98 Pathfinder.
I have done a little bit of wrenching over the years, nothing I would consider major but enough that I feel like I should tackle this job myself after seeing some DIY's and a couple helpful posts. Trust me, I wish it was just a tune up or changing out the fluids in the drive line or something but it is what it is. I honestly feel I can do as good of a job as any repair shop, I am not in a hurry, will take my time and go slow. In the end I hope to be able to help someone else have the confidence to tackle the very same project and save a few bucks as well.