I've just mounted my 50" Pioneer to a brick + plaster wall using the AV-Sales mount. I used six 10mm diameter Rawlplug mediumweight coachwork brickwork fixing screws (Rawlplug part number 67-674) and they hold the mount so firmly on the wall that a friend and I were able to
both hang off it at the same time, so it easily supports my 50" Pioneer and will have no problem at all holding your 42" Panasonic.
The screws come with the appropriate wall plugs, so all you'll need in addition to that is a 10mm drill bit and a hammer action drill.
Fixing the mount to the wall is a very easy task, but you'll want a friend there to hold the spirit level etc. to help you get the mount in the right place and level, and of course to help you lift the panel up onto the mount when it's securely screwed to the wall!
Good luck