I no longer have CFS1 installed. If memory serves me right, you can refuel at an airfield that has one by taxying into the yellow refuelling square & switching off the engine. Try some of Steve McClelland's scenery.
My list of essential downloads for CFS1 would have to include the QC Editor by Jaesen Jones. I would also have to recommend the Korean War series of campaigns I did with Mike Eustace.

There's so much good quality stuff available that it's difficult to suggest anything without knowing your particular interests.
FS9 will take some getting used to after CFS1. I suggest you wait until you have it before deciding on the best files to get. Things tend to move fast in this hobby these days. It will also depend on what you're interested in. TTools & AFCAD would be at the top of my list.