First, I will say that when you see the old timing belt, it will likely look just fine, if not almost new. Ignore this. Changing the timing belt is cheap insurance compared to what a failure will cost.
Second, this is not a job I would ever trust to a mechanic who cannot offer any warranty. If a Lexus service tech or Midas/NAPA/other-chain tech does the job and messes it up, you are covered. If this guy does it in his backyard or garage and messes it up, good luck. If this is your only route, you might as well set aside a weekend and do it yourself. If you or this fella screw up the job, you will have only yourself to blame.
I did this job on my Corolla back in '93 and it really took 2 days. Had to tear down the whole right front wheel area, disconnect a couple of motor mounts, remove covers, loosen tensioners, change the belt and reverse the whole process. Naturally, I knocked a pulley out of line and had to retime the whole valvetrain. Never again.