I need to know if anyone can send me the steps for installing hot and cold valve stems for a bathtub and if you can send a diagram of a normal bathtub bathtub and what each part is so I can help my brother-in-law and sister get their bathtub fixed. Please respond as soon as you can. Thanks.

We will need more info. Are you replacing two existing stems that failed? Most modern "stems" are actually replaceable cartridges.

Actually most stems are easy to replace, and many times the seats must also be replaced. It is however important to know what brand of faucet it is because some require special tools and procedures.

A couple of posts I made in another thread:

If it isn't too old and corroded, it is easy to pull the stem. Shut the water off, and for most 3 knob styles, pry the cap off, unscrew the screw, remove the knob, and unscrew the nut holding the insides. Inspect, clean, repair/replace. A good hardware will have cartridges to fit most brands and somebody to help you match the old one. I never go to Lowe's for stuff like that.

Some screws will not yield to a proper fitting, quality screwdriver. Heat works well on iron and steel. Even with them, I find hammering on things is often more quick. The trick is to hit stuff hard enough to distort it, but it still springs back without staying bent or breaking. When it moves, it breaks apart the rust, corrosion, lime, etc. holding it. A little spray lube helps too. I like silicone oil. I can use the same can to remove stuff and to lubricate things I don't want to gum up. It also doesn't swell rubber. The hammering opens up the joint long enough for the oil to wick in. You can put a good screwdriver with a tough plastic handle in the screw head and hammer on it. Often after a few minutes of that, the screw will back out. There are little hand impact tools that work great too. They take a bit or socket at one end and you hit the other end with a hammer. They twist when you hit them. Provides both the impact and the twist. If the head does strip or twist off without it coming loose, you can switch to a punch. Work at the edge pushing it in the way it unscrews. If the head twists off, you should be able to remove the knob. Then you can unscrew the assembly and carry it to your shop for further work if it is worth salvaging. A good hardware store is a better place for it. Match it to a new one. Note, hot and cold are not interchangeable. If the knob is worse for the wear or just old and shabby, theyhave new ones.

Doug is right about the seats. Cheap fixtures won't have replacable seats. If it didn't mean ripping up a wall, I would replace it with a single handle model.

How do I install tub shower valve stems

How do I install hot and cold valve stems for tub and showers

Actually most stems are easy to replace, and many times the seats must also be replaced. It is however important to know what brand of faucet it is because some require special tools and procedures.
What brand of faucet do you have?
Look here and find your handle http://www.kissler.com/catalog/Complete_Section_C.pdf

The diverter is old and the guy at the hardware store told me it needs a special tool

Hi Juanthorpe2

You'll need to provide us with more info. On the issues here, OK?

How many handles associated with the valve? What exactly are you having trouble with... removing the handle, for example?

The more info. You can give us the better answer we can try to provide... ;)

If you go to the plumbing page and look at the upper left hand of the screen you should see a NEW THREAD or ask a question icon... click on it and start your own thread... that way you go to the top of the page and more people will see it, OK?

Mark