I converted my 9A to a 9 last spring. Cost was about $2500: new engine mount and gear legs, tail assembly, new brake lines and some bits and pieces. If you got a quickbuild, the tail part is not a big deal - just pull a few rivets, a bit of trimming of the fuselage and put the tailspring in. If you did a slow build and did the lightening of the HS attach bars (F-711C) on the second bulkhead forward of the tail, then you will need to pull that part as well and replace (a bit more work as I understand - mine was QB). You will also probably need to modify the leg fairings - I just added some length to mine with some fiberglass. Probably will need the upper intersection fairings, although I just made mine so that the leg fairings come close to the fuselage and used some rubber stuff (leftover from the wing root fairings) to seal things up.
My engine mount fit the existing holes perfectly, and the cowling worked out so that I did not have to do any modifications on it.
Greg Vouga did a conversion on his 7A a bit over a year ago and was a good resource for me. Cameron Kurth also made a conversion. I can forward you our electronic conversations if you would like. Best to email me directly - my email is available in the user section of the forum.
I'm very happy with my changes, particularly when flying off of unpaved rough strips.
Greg
Obviously, Greg already posted while I was writing - and he needs to change his signature!