Yes, it's a bad Idea to purchase a trim kit that you like. without first Identifying the brand of faucet you have.

There are usually several alternatives for the type of faucet you have and changing them is a DIY project with very inexpensive tools.

You are aware that should the trim kit you like will not work and the material the plumber may have with him, do not meet your "likes", how much a return charge will cost. aren't you?

Thanks. Your post suggests that if I purchased trim of the same brand as the existing faucet, the two likely would work together -- is that [usually] correct?

It can be, however, there are several parts too a multi-handle tub/shower assembly, as well as the length of the stem extending out from the wall. There are also stem extensions available in several lengths.
Were I you, I would remove one of the handles, and with a picture of the faucet, go to a local plumbing supply, big-box or hdw. store, saving you the cost of the plumber doing it for you.

A trim kit has to match brand/screw holes, diameter holes, etc. exactly. So keep it if you don't know the right one.

Instead, I would take a handle off to go match it. If you're lucky, it's the handle that needs replacement - if you're less lucky, it will be the end of the stem that's stripped and then stem would then have to be replaced.

As for the leak, I suggest you do let the plumber do the leak repair. You could observe to learn how to do it next time. Sounds like it needs a stem washer or something like that. (pics would help). Take a handle off and have a look. (Hint: First cover the drain with a cloth so you don't accidentally drop any screws down there.)

Same for the other faucets. If they're leaking, they need parts. Plumbers aren't cheap, so observe the repair closely so you can do it yourself next time.

Another option is to post some pics. We might be able to identify them. then you can start youtubing the repairs...

This post was edited by homebound on Mon, Dec 9, 13 at 7:00