it's just about as easy as dragonfyre put it. one word of advice: be sure to torque the harmonic balancer bolt properly. my mother-in-law has a cressida 5mge, was complaining of lack of power. i pulled the timing belt cover to inspect it, and it looked ok. i turned the timing gear by hand to line up the timing marks to check wether the belt had slipped. the belt tension was good, both timing gears turned, but the crank gear had about 20 degrees of slack in it. turns out the hack mechanic that worked on the car before she bought it didn't torque the nut properly and tried to use sealer to hold it on. i was able to remove the bolt by hand :!: not only that, but woodruff key had eaten a grove into the crank pulley :!:
i was able to get parts from the local bone yard to make repairs, but replacing the woodruf key without removing the crank was quite a challenge.
you need to be able to hold the crank to torque the bolt. i pullled the access cover at the rear of the engine and wedged a big screwdriver between the ring gear and bell housing. other than that, you should have no problems.