For use motor oil analysis I use Blackstone labs - http://www.blackstone-labs.com/ - their standard analysis cost $25.
As for how long the car will run to, all depends on maintenance and a little bit of luck. Not knowing the history of the car makes lifespan determination very difficult. Even if you jump on all the maintenance requirements from now on, depending on what happened in the past - you may or may not hit 200K miles or more. Used motor oil analysis and some other tests, like compression testing, monitoring oil consumption, etc. should give you some idea of what the car is doing.
As for the cap and rotor replacement interval - depends on how the system looks. Generally, your plugs will last between 10K-30K miles for copper plugs, about double that for platinum plugs. Stay away from multi-pronged plugs like the Bosch+4 or similar, works great in other cars but reported to run poorly on Toyotas. Bosch single platinum are great though, but personally, I'd only run NGK or Denso plugs in the Toyota - proper reach, heat range, and known performance.
As for services, there was a pretty through discussion on this forum before, I don't remember the link off-hand, but you should be able to search for it.
Definitely stay away from transaxle flushes, unless they hook it directly to the pump, not suck it through the dipstick or backflush through the cooler lines. You'll know it is the better one if they have to drop the pan to do it. Timing belt - replace every 60K miles to be safe, waterpump, timing belt tensioner, and accessories at the same time as well, since all that stuff has to come off anyway to get to the timing belt. PCV valve every 10K-30K miles, depending on how much blowby you get. A quick test is the rattle check, remove PCV and shake it, if it makes a rattling noise, it is still good. But replace it at 30K miles, regardless if it rattles or not - as the spring inside can get tired by that point. Don't forget the other fluids - powersteering (every 30K miles), brake fluid (every other year or 30K miles), coolant flush (use distilled water and Toyota OEM coolant for longer life - every 60K miles, timing it with a waterpump/timing belt change is a good idea). Fuel filter - every 60K miles, good fuel injector cleaner once a year (Redline, Gumout Regane, etc.)