In my honest opinion, you MUST get the car examined by a BMW specialist, be they a dealer or not.

There really are just too many things to look at to give you a do-it-yourself check list.

It would also be advisable to talk to the specialist or BMW to determine if yours was a Nikasil engine. My understanding is that the 2.5 and 2.8 engines sold in the UK in the E 39 up to the 10th week of 1998 were Nikasil engines and suffered greatly if exposed to high sulphur petrol. For more info do a search but a phone call to BMW should settle that issue.

Do a search on Niaksil on this forum and all will be revealed.

If Nikasil is a potential issue, a leakdown test will be required.

Therefore getting the car looked at by an expert is, in my opinion, essential.