1) I believe you can add Sirius to your existing radio with an external module. This could be less work and expense.
2) The wiring diagrams for your coach (link here
) includes a "Front End Wiring Installation" diagram set (link here
). Sheets 7 and 8 of that set show the radio installation wiring (two versions).
3) Based on the diagrams, I'd say the connectors are AMP/Tyco/TE Connectivity Universal Mate-N-Lok 1 or Universal Mate-N-Lok 2 style. You can buy the components at Allied Electronics (link here
4) A picture of the existing connector would help.
You should add a signature to your profile. Most people include the make and model of their coach in the signature; some add other information useful for others to know. The signature is added to each post, so you don't have to type that information. You set up a signature by clicking on the "User CP" option (upper left on orange banner on each page) and select "Edit Signature."