The phrase 'voiding warranty' is greatly overused.

What happens when you modify a vehicle is that if you have a subsequent failure that is caused by or accelerated by your modification, as judged by your dealer, then the repair isn't likely to be covered. It can depend a lot how good a relationship you have with your dealer service advisor.

What can be impacted by lowering the vehicle? Any problems involving the suspension, steering system, tire wear, or alignment issues could be up for debate. Obviously, the new parts you install won't be covered (but they should be covered by the shop that sold them to you). The rest of the vehicle won't be impacted.

Will your dealer install the lowering kit? Unlikely in my opinion, but you can always ask.

__________________
2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue