Replacing shower knobs will it help?

Whoever's replacing the washers should also be replacing the faucet seat (the thing that the washer contacts). If the seats are rough it'll eat up the washers. Sometimes the washer cups are deteriorated. If that's the case, replace the seats and look for 'no-rotate' faucet washers. You'll have to remove the rest of the washer cup.

If by replacing the 'whole knob' you were referring to the faucet stem (the assembly that has a handle on one end and a washer on the other) it /might/ help if the above-mentioned cups are bad. You should replace the seats in any event.

If by 'whole knob' you meant the handles, that won't do any more than make it look pretty again. And there's nothing wrong with that.

The washer makes contact between two pieces of brass or copper.

It sounds like the brass or copper is no longer smooth, but has been chipped or damaged, and that chip is tearing the washer to shreds.

A quick trip to Home Depot will reveal that little cylinders of copper can be purchased (I think they might be called "valve seats" - for about $4 CAD. You'll need a corresponding wrench, $8.

Quick and easy fix. Just put the plug in the drain first, so no pieces get lost down there.

Replacing just plastic knobs will only make it look pretty. Replacing the whole faucet is more work than necessary, and will require some copper soldering skills. Possible for a homeowner who is (or could be) mechanically inclined.

turn off the water to the house*, find the screw that holds the handle on the valve. After you remove the handle there should be a part of the assembly that looks like a large nut. Turn that counter clockwise** with a wrench and you'll be holding the valve assembly. take that into the hardware store and ask if they have a replacement. At very least you can now replace your own washers. ask the store ppl to show you have to do it.

*turn on the hot water for a while after you shut off the water, the water heater needs to depressurize

**if it doesn't want to turn then tap on the wrench with a hammer instead of pushing harder, otherwise you could break something.

Plumbing screws are most likely made from brass so, will have to be effortless to drill out provided you may have a small 1/eight" sharp drill bit and a good eye to drill via the center. Or, if there's any protruding you could reduce it on high with a hack noticed so you have got an I so that you could put in a flat screwdriver. Otherwise, rip out the shower.

nope