I have a Mixet shower faucet (MDXTR-5) (http://www.plumbingproducts.com/mixet.html). In the last several months, the cold side of the faucet has been having a very low water pressure. The hot side has a good pressure. The house is 11 years old, and I've lived there just for a year, so I don't know for sure how old the faucet is.
I found another post (https://www.askmehelpdesk.com/plumbing/low-water-pressure-cold-side-shower-faucet-14347.html) on this site, that suggests there may be a blockage in the faucet.
Since the shower pipes are inclosed in the wall, and there is no valve, would I need to close the watter supply to the house in order to open up the valve and pull out all the parts? I heard that putting all the parts back together into the wall may be tricky. Is this job too complex for a lay person, or is it worth calling a plumber?
Thanks

It is never a bad idea to call a plumber but many projects can be done by a homeowner. There is most definitely a valve. First shut off your main and drain down the water by opening a faucet in a lower part of the house. Remove the faucet handle whether it is a single handle or two handles. Once the handle is removed you should see a brass nut shape valve stem. Yes you can screw up the pipes inside your wall but rarely this connection. There are several pipes and probably a mixer in the system all adding to the strength.

This particular model should have integral stops cast into the body of the valve, just behind the large round escutcheon plate that you can turn off with a flat blade screwdriver -- You'll need to remove the volume control (the outer knob) and the temperature setting handle (the inner blade handle) You'll then need to remove the round sleeve with a crescent wrench.

The cartridge can then be removed by gripping the stem tightly with a pair of channel locks and pulling outwards.

Once you get the cartridge out, you should slowly turn each stop on, one at a time, just long enough to flush out any debris before installing the new cartridge.