Originally Posted by Clockwork

Remote needs to be re-programmed. Thats a 3 second job you can do yourself (get inside vehicle and close all doors and windows, put good key in ignition and turn to accessories 1 position for a second or three, then turn off and remove key. Hold unlock button down then and press lock button three times then let go all buttons. X5 should lock and unlock doors to confirm vehicles locking module and that key are now synced, so now sync the other keys by pressung buttons on that key same ss first key.

Drivers front window probably needs window regulator slider clips and window clips replaced. Cheap and relatively easy 3-4 hours for first time.. lots of videos on youtube and even discussions here. Parts to get and where from.
I know cause i just had to do this a few weeks ago and the key programming too funny enough.

Missing buttons can be replaced by you too easily

The rear airbag suspension most likely needs a new Arnott (Brand name) airbag. Easy job i hear and sbout $300 for parts and shipping with lifetime warranty.

Constant beeping pdc means sensors stopped working. Amazon and ebay sellers selling sensors which looks exactly like bmw sensors for about $15-30 each. Easy to install. You just need to learn how to remove bumpers. Easy to do the front. And to lesrn WHICH sensors you replace, turn vehicle onto accessories 2 position and turn on pdc button and put your ear to each sensor 4 front/4 rear and listen for high speed ticking. If they tick, they work.

if my spelling sucks in this post its cause im typing on a tablet.