The extend-a-stay kit is attached between the main tank and the regulator. On my 94 LY I did not have to remove the cover. My suggestion is to have a gas tech do the install. Firstly, he will know exactly what has to be done and secondly (very important) if anything goes wrong and a fire is started, your insurance will bail out.
I had the kit installed initially by an RV tech in Casa Grande, AZ. However, I there was always a lingering odour of gas. When I got back home to Canada, my friend who is a gas tech redid the connections and the odour went away.
Unless you *really* know what you're doing with gas, leave it to the professionals.
1987 Excella 32-foot
1999 Dodge Ram 2500 Diesel