1st, When changing to mechanical tappets rather then hydraulic, do you have to change anything else apart from the cams?? ie guides, stem seal etc

and 2nd, if im fitting a set of gauges and i want to be able to dim them on the same circuit as the rest of the dash,(hope this makes sense) does anyone know what wires i need need to connect to off the back of the dimmer switch?? (its a three door cossie if its any help)

many thanks for any info