Replacing old American Standard

hot/diverter/cold handles on a tub as well as teh tub spout and shower head.
My question is:

Should I hire a plumber or attempt to do it myself? I am ok with sweating copper but have never done a pressure balance valve. Can I use PEX to do this instead of tearing out the wall? (never worked with the stuff)

If I tear out the wall can I go down into the crawl space,cut off the supply and build the thing up at my work table and then just make the one sweated joint in the crawl space so as to have the space to work on the stuff and do it right?

Finally,I plan on using GROHE. Any thoughts? What is the difference between a 3-port,4-port,3-port with stops,4-port with stops valve?

Thanks.
Alan

To properly mount a new valve, you will need access inside the wall, either from the front or back side.

Depending on the layout of pipes and studs, it is possible to preassemble some of this, but you still really need to be inside the wall. A good plumber can sometimes replace a valve just working through the hole in the tile or fibreglass. It is very difficult, not a DIY project.

If you use PEX, there is a whole new field of knowledge you need to study up on....fittings, tools. And, remember this: PEX sizes differently than copper, and if you use PEX to install the tub spout, you will be posting back here to ask why water comes out the shower head when taking a bath! We get that question about once a month on a regular basis!

Thanks. I think I will let the plumber do it this

time. I am ok with tearing out part of the wall since I am going to retile it anyway and will cover it up with Hardi. In a pinch I could also go into the wall from behind but I will let a pro do it. I am not all that comfortable sweating the valve.

I forgot the other part of the question--what is the

difference in these valves : Grohe pressure balance
3-port
3-port with stops
4-port
4-port with stops

Thanks.