My plumber told me my water pressure is too high and is ruining my fixtures. Apparently my house is old and does not have these. Is installing these valves something I can do myself? The plumber wants to charge me $500.00. If so, where can I get directions? Help.

Ball valves and Pressure valves are two different things.
Watts Pressure reducing valves(PRV) can be purchased at any plumbing supply store.
Don't know why he would switch to ball valves unless you have to replace them anyway.
Installation of a PRV is fairly simple and each package has simple instructions.
If your on town water check with your provider. If the pressure is too high in the area they may supply and install the Pressure Reducing Valves.
In my area if the pressure is above 80 PSI the Municipality installs them.