The car has a timing chain. Search the Shop Forum archives (search function in upper right corner of screen) for other 240D references, discussion, and tips. I'm not sure how much of a DIY'er you are but if you are unfamiliar with the motor and associated systems it is never a bad idea to take it to someone who knows the motor by heart. Even to just help familiarize you with everything.... Sort of a "post-purchase" inspection. That would give you some good DIY projects and guard against "engine killers" for the short term.
As for what could be wrong (without seeing it, given its age, described condition, etc) You can probably trust the oil, everything else is suspect...j/k It is hard to say without seeing it in person. 240D's run forever, but nowhere in a hurry. 0-60 in the 25-27 second range is quite normal. If there is anything else you need please feel free to ask.
Hope this helps...Lee