Hi, Pascale -
BAHAs are wonderful
Got one myself just recently - had the implant surgery at the beginning of March and got my processor at the beginning of June.
Some doctors combine BAHA implant surgery with AN surgery, but some don't; it pretty much depends on the doctor. I had my implant about 9 months after my AN surgery. BAHA surgery is nowhere near as difficult as AN surgery - I had my BAHA surgery with local anesthesia and was awake the entire time, and even if you choose to have general anesthesia it's an outpatient surgery - so if you don't have a "combined" procedure, don't stress about it.
BAHAs generally are placed in the same spot and from what I know, AN surgical approach has nothing to do with placement. I had retrosigmoid surgery, Lori67 had translab, but I believe our BAHAs are basically in the same place.
I recently posted pictures of my BAHA on this forum. Here's the link if you're interested http://anausa.org/forum/index.php?topic=6634.msg65388#msg65388
If you are seriously considering the BAHA, try out the demo (basically the processor attached to an elastic headband). I found it very impressive and it's what ultimately made me decide to go with the BAHA.
If you have any more questions, please feel free to ask me.