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"And the three front seals being...?"
- Front main seal (crankshaft).
- Camshaft seal.
- Intermediate shaft seal.
"How involved are replacing these seals?"
Not very. You quite literally remove (pry out) the old seals and insert the new seals in place. You must be sure to drive the seals in straight -- some folks use a piece of square-cut PCV pipe to do this (good idea), but I've done a zillion seals using a flat drift punch. You also must be sure the seal lip doesn't "roll over" when installing, and be ABSOLUTELY sure to lube the seal lip and mating surface with clean oil. (A dry seal lasts about 2 revolutions of the engine...)
Getting to the seals requires that you remove various sprockets and stuff -- this is probably the time to buy a Haynes or Bentley manual that shows details of this using illustrations.
"Water pump looks OK. What are its typical failure modes?"
Often the bearings wear so the shaft can wobble and then the seal begins to weep. This results in antifreeze dribbling down the front of the block. But also, the top ("mushroom") seal can fail, usually as a result of a bad cam seal, which oil-soaks the rubber water pump seal. And the pipe O-ring can leak when it dries up.
In rare cases (with brand X pumps) the impeller blades can corrode away and the pump won't pump much. (BTDT)
"Valve cover gasket looks fine, no sign of oil seepage; since this can be done fairly easily and independently of the timing belt job (please correct me if I am wrong)..."
You're right. Moreover, no need to diddle with the valve cover if you pry out the cam seal.
I would estimate that, if you already have the front apart for a timing belt, replacing the seals will add about an hour, depending on your skill level.
I personally prefer to remove the seal housing (crank seal) -- about 6 small bolts, two up from the pan -- and install the seal in the housing and then reinstall the housing with new seal over the crank. Others remove the seal leaving the housing in place.
--
Don Foster (near Cape Cod, MA)
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