Hi Groni,
I've had a AA-ES converted to a 2010 version. Best way to do it is to call Taylor for an
authorized tech nearest to you. Mine came out perfectly, not to mention you buying the 2010 preamp/harness from Taylor and then paying for the work performed locally is far less costly even with the minor woodworking necesssary with the AA compartment (not to mention less stressful as you don't have to ship your guit) than the factory performing the work. As a reward for your trouble, you will have the improved tone of the current-generation ES as well as having the trouble-free 9v battery compartment over the pesky AAs.
OTOH, if you are the guitar's original owner, then your ES is covered under warranty. If they accept it, then they will likely replace your 1st-gen with the 2nd-gen ES (the 2007-2009 9v system) so you won't be getting the newest ES, but will still be a vast improvement. You will be on the hook for shipping costs, but at least you'll get a great sounding amp'd tone in return
Edward