Hallo there, all great, thanks mate!
It is pretty easy to install them, the big difference is that the old, original piezo had just a single wire, going to the motherboard, while the graphteck has 2 (hot and ground).
The hot you connect them to the motherboard (same positions as the original) while the ground you sum them to one (all together) and solder them to the grounding of the variax (honstly i made this operation 11 years ago and dont remember were was the grounding of the instrument) But i remember, that the blue wire was the hot, and the nakes the ground. Dont know if they changed the wires color after all these years, but i dont think so.
Pretty easy to do alone, you need soldering iron, a screwdriver, and you are ready to go.