Hi. I am new to the club but not BMW's. I bought a 1996 e38 740i two years ago. The owner kept it in a dehumidifier for long periods. The car had done 77k only and came with individual champagne NAPPA leather piped on black and 20" alpina soft line wheels. My top for buying is take your time and ignore the hype on some forums re changing the gearbox oil. Just find a brilliant independent who will re set the box to accommodate the pressure from the new oil. Finally, if you don't use it very often then make absolutely sure you have it on trickle charge it you will end up with all manner of electrical glitches, especially the radio.
