I will do the following if I were you...
1. Get the VIN number.
2. Log on to
http://www.bmwarchive.org/vin/bmw-vin-decoder.html to check the car specs, YOM and etc by key in the last 7 digits of the complete VIN number.
3. Check the details of the service booklet at the trunk.
4. Get the car reg. no. and call to the respective authorised dealer to check if the car still under BSRI (3 years or 5 years).
5. Send the car preferably to the SC that has the car service history for inspection. Usually you will be charged about RM200-300. Join the mechanic to 'listen' if the timing chain is good. Search YouTube for N47D20 timing chain and you can get lots of useful information.
6. Check the price for those parts listed in the service report. If those parts are not covered under BSRI and it is due for replacement, you may try to nego a better price with the 2nd car dealer.
7. Get second opinion from competent BMW workshop and do an inspection again. They will usually drive the car around to check if the gearbox is ok. But it is purely based on their experience. No 100% guarantee.
Usually the car dealer will ask for deposit before sending the car to the designated SC.
If you decided to make the purchase, next thing to do is to replace gearbox lubricant and oil pan, even they say it is for life time. Don't flush the gearbox. Some fellow forumer said problems might surface after flush. If you worried your BSRI void, then you can choose to change after 100kms. But I don't think they will know as long as you use genuine oil pan.
My 2 cents.