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Replace the valve seal and check the valve guide for wear.
http://www.kick-fix.com/t-belt/tbelt.html
Pull the engine.
Replace valve seal
Its called a valve cover gasket kit and the job should cost about 300.00 Parts and labor.
The right seal can be replaced by only removing the right shaft. To replace the left seal, the entire axle needs disassembled.
The head, or top part of the motor, must be removed to replace valve seals. After the head is removed take it to a machine shop and they will mill the head to make sure it is flat and also grind down the valves and replace the valve seals.
Remove the trasnsmission and you can then replace the seal.
Do a valve job. This is more complicated than it sounds, you might be better off sending the head to your local machine shop for the valve job.
What type of rear end do you have?
Oil Pump Check Valve. Replace oil pump
The transmission must be removed. Not a DIY job unless you are skilled.