Leaking shower diverter

Can someone give me a heads-up and/or link to more info on a DIY repair.
I've got a combo tub/shower with a common three-handle arrangement, the center handle switches from tub faucet to shower. Unfortunately there's no brand name in sight. I've replaced the rubber washers in the hot and cold valves numerous times. Lately, the tub faucet dribbles a fair bit in the shower position. I think it's getting gradually worse and I'd like to fix it.
My shower is tiled, and there's no easy access to the back side of the plumbing; the other side of the wall is in a closet, covered with drywall. I'm hoping to get some knowledge before attacking this. Is this a reasonable DIY repair? Simple like a washer, or hard like replacing the entire valve assembly? Will I find repair parts in the big box or hardware store? Can it be done from the front? If not, maybe by breaking though the drywall on the other side of the wall? Is this going to lead to a bathroom remodel?
TIA, Joel
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On Thu, 17 Jul 2008 06:02:32 GMT, default

Joe, Why do you want to break through the back or side to tackle this problem? Its the same as replacing the washers in the hot and cold faucet. Pull the stem. Then you can rebuild it with washers, o rings, etc. Dont forget the set back in the body. Replace it too. You can also just buy a whole new stem instead of rebuilding it. The big box stores may have it but finding help and getting the exact match there may be challenging. We have several specialty plumbing stores in my area that are wonderful. Bubba
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As mentioned in another post--go through the closet wall to get at the shower hardware. Same setup in my closet except when built they put a piece of plywood over the opening to serve as an access to the back of the shower plumbing. MLD
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See #11 in this diagram. It will give you an idea of what the cause is. For this particular Central Brass one, it is called a Celcon Washer. Looks like just white nylon.
http://centralbrass.com/documents/PARTBREAKDOWN/B0950.pdf
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On Thu, 17 Jul 2008 06:02:32 +0000, default wrote:

Thanks for all the suggestions, esp. the diagram!
-- Joel
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