so I wound up doing the Autocraft battery (manufactured by Johnson Controls like a lot of other batteries - I seem to have bought the very last one on all of Long Island says their website) and got it put in. Battery $148 + install & registration by a local indy $125 = $273. They also mentioned they had to reset the sunroof module as part of the process. Anyway, this was more a stay-away-from-the-dealer more than a DIY, but hey, still cheaper. Thanks for advice in this thread.

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'08 X5 3.0si - Alpine White / Saddle Brown interior
Specs: Sport Pkg, Premium Pkg, Tech Pkg, Comfort Access, Aero Kit, Style 433 staggered 20s on Conti DWS
Mods: Carbon 35 tint, LED angel eyes, GP Thunder 7500k fogs, H&R 20mm/25mm spacers, clear reflectors, gunsmoke-tinted taillights
Coded: Digital speedo, windows/sunroof/tailgate close via keyfob

X5 pics at Flickr