Actually, one of the nice things about Randy Steele's kits are that he does all of the little things to make it easier. The wires are all labeled, where most people will send you the wires and you have to figure them out. He also includes all of the wire guides and clips, not as big of a deal for the M103, but a nice touch nonetheless. For the M103, he'll includes your choice of either the suppressor housing or cover, since one of them is usually broken. He also throws in a little bit of di-electric grease.
I was very happy with his kit for my M103, I wish I'd bought from him for my 560.
And he uses only OEM parts. Beru connectors with solid wire cores, Bosch plugs/cap/rotor.
1988 560SL Black/Palomino
1988 300SEL Black Pearl/Burgandy
1984 500SEC Anthracite Grey/Palomino