Sorry to hear, beautiful looking X5... If the cost is about $4k-5k and it will make your ownership of this car last 2+ more years, that is like $200/month... kinda sorta worth it if you consider the lease monthly payments on these.

Also, from the posts above, I can't figure out if the fluid/filter change was done before the transmission stopped working, or after, or both. I personally am of the opinion that a fluid change CAN cause more problems than it may supposedly prevent... I changed the fluid/filter on my previous MB C240 at about 75k miles (MB also said fluid is lifetime and no need to change)... and the transmission in my car started to act up when cold in the morning and some other stop/go situations and such. Needless to say, I won't be changing any transmission fluids when the manufacturer doesn't require it, but it would be nice to know about your scenario regardless.