I've done this one. The new "water pump" in your hand is the insert
which bolts into the water pump's housing. The only thing that's really
new is its bearing and seal. So that you'll appreciate your mechanic's
offer I'll describe the job.
You'll need some metric sockets, a short 4" or 6" extension, ratchet and
open end and closed end wrenches. If you lack these and feel that they
are "instruments of the devil" have the mechanic do the job. QED
The water pump is located on the front of the engine, behind the belt
The coolant must be drained into a pan; the drain plug is on the bottom
of the radiator, on the left. You get to it by lying under the front
bumper. If the coolant hasn't been replaced in years it should be.
The drive belt's tension needs to be slackened; that's done at the
alternator. Its mounting bolts need to be loosened (only) so the
adjustment screw can move inward to relax the belt. You'll be plenty
dirty after this.
Remove the top radiator hose from the thermostat (water pump end) (only)
and gently stuff it somewhere out of the way. Now comes the tough part.
There are four or five small bolts on the front of the belt driven fan
hub that need to be removed. The work space between the radiator core
and bolts is tight and the bolts are tight. Some people remove the
radiator. IT'S VERY EASY TO ROUND THE HEADS so be absolutely sure your
closed end wrench is the exact size and fits perfectly. If you round one
of them the job is lost to the mechanic after a tow to his shop. Remove
the fan and hub; stand the fan vertically - don't lay it down. Now it's
time for the water pump.
Your car's engine has a large harmonic vibration damper with a cut out
portion that you need, so rotate the engine with the key or your hands
so its cut out allows your socket access to the water pump's lower
bolts. Use a socket to remove the five or six bolts that secure the
rotating core from its housing. Remove the core and scrape the gasket
surface of the housing clean so the new gasket will seat and not leak.
Install the "new" pump with the gasket in place; the pump mounts only
one way or the bolts won't fit so that's easy. Torque the bolts to about
20 ft lbs.
Reinstall the fan hub and fan, tighten the new hub bolts with a closed
end wrench as tight as your hands can stand. Reinstall the drive belt
and tension it at the alternator, secure the alternator's mounting
bolts. Reattach the upper radiator hose to the thermostat end. Replace
the radiator's drain plug and refill the coolant.
This is the job. It's not mentally difficult but has a few nasty bits.
IMHO your mechanic is earning his $270 for it requires tools and takes
at least two, if not three hours to complete. And remember, he has to
deal with any rounded bolts etc. I found the bent over position of the
job gave me a sore back for the next two days.
Happy New Year