For even tire wear, I'll have the tires rerotated to the Sears position. Why would the dealer rotate at A service anyway? I thought it'd come at B service - anyway it really depends on the mileage on the tire.

Yes the tranny is sealed for "life". No, your warranty will not be voided if you replace the tranny oil at the dealer. As a matter of fact, you can have it done anywhere you want (use certified shops of course) and that wouldn't void your warranty - in the US, at least. BTW, what mileage and why even want to service tranny? If under 70-100K (and it sounds like you are), don't bother. I'd say change the fluid along with all the other 4-wheel drive system fluids at around 70-100K.