This product states "easy installation" but it is hard to determine if a do-it-yourselfer can do it or should it be done by a plumber?

If you are replacing your hot water heater you can put this in without issue.

The link below will give you all the information you need to determine if you will be able to install this yourself. This page contains links to a very detailed installation video, as well as the actual installation instruction manual included in the box. http://www.watts.com/pages/whatsnew/IHWRS.asp

First of all, your new water heater should come with a pressure relief valve already installed. In some states it's illegal to install your own water heater without a licence. Now that all of that is taken care of, It's easy to install once you have drained your water tank to the proper level. The hardest part is the preparation. Lots on video and information on the net.

If you are personally doing a hot water replacement then this is a no brainer, you will definitely be able to do this. If you would be comfortable replacing a kitchen faucet then you also have the valve side covered too. Only thing else you'll need it an outlet for the power to supply the pump. The current draw of the pump is very minimal so a heavy duty extension cord could be used if you don't have an outlet right by the hot water tank.

I don't see why not, the material the pipe is made from should not matter as long as you can adapt the pump to it.

I had more trouble installing power to it than anything else. That is because I wanted an outlet with a pilot light and on/off switch. Installing the pump was not hard using flexible connections and the valve kit for the farthest point was not any real trouble to install. I have told my wife that I would rather walk on broken glass than tackle a plumbing project so when I say it was no real trouble I mean it.