valve guides on 2000 Toyota Celica

Can valve guides be replaced on a 2000 Toyota Celica, 1.8 liter 4 cylinder? If yes, how difficult is the task?

Asked by for the 2000 Toyota Celica
Yes valve guides and seals can be replaced, cylinder head has to be removed and a "valve job" done afterward, and timing belt replacement would also be recommended. It's a day's work to remove and refit the cylinder head. Doing the valve job or fitting a reconditioned cylinder head incurs additional cost.
We just bought the car 2 months ago. 1 month ago the O2 sensor went out on it. Since then the car has used 1 quart of oil every 500 miles. I have replaced the PCV valve. No noticable oil leaks. Car runs great. Not sure if the car was using oil when we bought it. Car has 145,000 miles.