Welcome and your X5 looks to be in great shape!

As far as the warranty goes, in my opinion you would be better off setting that warranty money aside for when something does break. The big the is the transmission, but you could find a used one for the cheapest fix, but the rest of the things are just nickel and dime stuff. Things such as window regulators, door handles, cv boots, suspension bushings, etc. The two bigger things you'll experience on a pre facelift is a t-case chain replacement (they stretch over time) and the abs module failing (usually a ~$120 repair, but requires you to send the module out).

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03 3.0i mt
89 325is