I replaced the one in my '97 this fall, it was a challenge.
Take the intake hose off the turbo intake, then zip-tie a rag over the turbo inlet.
I did mine without removing the oil filter.
The screw in the middle of the heater would not start, of course.
I found a long drill bit so I could run it out by the inner fender and drilled the head off of the allen screw.
Then you find a fairly long punch that will fit through the screw hole and whack it until the fingers behind give up.
Then you have to work the old block heater back and forth in the block until the o-ring around the outside gives up and lets go of the casting.
I used the new block heater as a guide for drill and punch size, etc.
I will be around all day so yell if you have trouble.
Mike.
