Are the valves and TPMS one unit?

They are integrated with the TPMS. The tire store will sell a service kit that probably just replaces the sealing rubber ring.

 

They only change the tires, they shouldn't be messing with the valve because its a unit on the rims. There is no need to change any gasket on the valve since its a torque down unit and no need for recalibration. Also, if they charge you for the valves, I would suggest they better remove the cost because you never used their rubber tire valves.

 

This is what they try to sell you which you can decline.

Many salespeople, whether due to deception or ignorance, will tell you that the kit includes replacement batteries. This is not true. The TMPS batteries are potted in permanently.

http://www.discounttire.com/dtcs/brochure/general/tpmsRebuildKit.jsp

 

I just replace the tires.
If the tire shop wants to replace the stems, and it's included in the replacement package, that's OK.

TPMS isn't emerging technology.
It's been mandatory for all cars for something like 8 years now.

Most cars now have receivers that will tell you which tire is low ("my" 2010 G3 does not, my GMs do)
There's a calibration procedure that allows the car receiver to 'learn' which TPMS receivers are installed and where they are.
This is very handy if you're one of those poor souls who live in the Frozen North and have to contemplate snow tires!
How to Reset the Tire Pressure Sensor
- CarsDirect

None of this should be necessary when you replace your tires.
The life cycle for most TPMS sensors is at least 5 years...and if your tire place offers to replace the valve stems (necessitating removing and re-installing the sensors) then they should explain to you why this is necessary (lawyers) and how much it will be.

Some shops charge a nominal fee ( like...$5 per tire) to RESET the sensors, which is different from replacing the stems.
TPMS resets can usually be done either manually in about 10 minutes or with a scan tool in less.
In some shops, $20 is a fair labor rate for 10 minutes of labor.
I'd pay it.....if I knew what I was getting and didn't feel like dragging out the compressor.
With my GM's however, I'm not that anal.
I just want to know that all four tires are mostly inflated to specs, and I usually don't bother to check that each corner has been properly registered.
I use my TPMS as a 'trip-wire' system. Since I semi-regularly check my tire pressures, my TPMS only has to tell me that something is wrong. I'll take it from there.
If my TPMS tells me that one tire is low?
I'm going to check the other three!
Besides....checking the location of each TPMS sensor requires almost all of the work that is required to reset them, and if I find that two of them are in the wrong place I'll have to reset them all over again anyway!
Life's too short to bother with all of that!

Usually, I'll buy my tires either at a big box store or at a local tire shop with a VERY trusted wrench.
At either place, I get an OTD price for all 4 tires.
That makes things nice and easy and I don't have to sweat the details.
Most of the big-box places also offer an install package that pays for everything including pro-rated road hazzard and (most importantly!!!) free rotation and spin balance every 5,000 miles, which is very important if you buy 60,000 mile tires and plan to get all 60,000 miles out of them.
Both of the places that I buy tires replace the stems and reset the sensors.

YMMV.


Good Luck!