thanks for the bouquet brooze theres always new to find out and learn though,you can still get the 500 induction rubber parts,they are important to be in good condition with no cracks and leaks,,i know you have a bad back and hope its well enough to do some bending/stooping and light lifting on this bike,,a quick run down to get this an easy starting well running reliable bike before you even try and start it would be.
empty the fuel tank,clean the filter screen in the little bowl on the tap
remove the carb bowls and remove and clean the jets,with the floats and the float needle removed gently blow compressed air down the fuel lines,with the air screw removed blow gently air into that hole aswell.
replace the air filter,dump the oil and filter aswell.
when the tank is off,undo clean and reconnect every wire connector you can find,look for tampering like black tape and twisted together wires or black burned wires,same behind the left side cover.
dissmantle the points assembly and if the points dont look burned or pitted put it all back together gapped and timed,new spark plugs aswell,you said your not big on electrics so if you have a buddy to help dont take apart what might be confusing to reassemble,after all that you could check it for spark and go from there,good luck.