Okay, so I bought the car of my dreams: a brand new 2001 X5. How sad I am to report the numerous times I've had the car in the shop: door handles with chipping paint (the new ones chip, too), passenger side mirror not tilting down in reverse (twice), water pump breaking, and what may just be the deal breaker: something in the cooling system exploded, causing a large hole for the coolant to exit through. Since my 3.0 has no coolant level gauge, the only thing I noticed was my car dying on the freeway.
Hey, BMW, after regular scheduled maintenance, shouldn't an engine on a $50,000 car last more than 63,000 miles??? Don't turn me into a BMW widower...

I'm sorry to say that there are only a couple of things that will kill a M54 engine. The main things are lack of oil changes, improper oil filters and/or oil, and overheating.

Don't ask me why BMW thought it was a good idea to leave the coolant level sensor out of certain cars. I feel bad for you but in the end, it's the driver's responsibility to look at the gauges from time to time. I'm not saying that I drive down the road constantly staring at my fuel and temp gauges but I'm not going to blame my car for not flashing up a message that tells me to add oil, or fill my gas up. That being said, it's a very common problem to have a water pump go bad, you are lucky the bearings did not blow apart and shove the engine fan into the radiator. It's also common to have the belt tensioners blow apart, t-stats stick and cause overheats or CELs, or the coolant expansion tank to explode. (Been there, seen all of that before) I don't know what kind of cheap german plastic BMW uses in their cars but it all explodes when the cars get older. Whenever any of these components fail, it's usually just a matter of replacing the failed part, refilling the cooling system and off you go.

If you lose your coolant and continue to drive until the engine melts down, there is nothing that is going to make that engine last any longer, regardless if it's installed in a $100,000 BMW or a $5,000 Kia.

I have replaced several engines under warranty after the customers have killed them by not stopping the car in a timely manner. If you purchased the vehicle from a dealer and/or you have a good relationship with your local dealer (like if you do all of your service there and spend $$ or buy a bunch of cars from them) they MAY be willing to give you some assistance towards the repair but there are no guarantees.

I'm also sorry to say that the other problems that you are describing, such as the door handles and mirror (you probably need a seat module or mirror motor) are common issues on X5's.