The special cable goes into the secure connection and has some blob in the middle of the cable.
You can program via RS-232 on the rear connector, and I don't have that info handy anymore once I got the special cable. I did find it on the web, so try repeater builder, bat-labs etc. You may have to check the MLM to be sure it's setup for RS-232 or change jumpers.
AS+ are bastard radios, which mother M always makes by screwing up a really good radio like the AS as a holdover until the next generation. They did the same with the MX-S. Early ones were terrible, but the green boards were really good, and I bought a lot of just the boards NIB for projects like updating MX PT'S from crystal to synth.