It should be fairly easy to write an interface to RS232 and then process the packet data - I'd do it if I had time., though the 38-pin diagnostic interface is very basic - I'm not sure it's worthwhile going down this route (the US got OBD2 in 1996 on the R129).

Keep checking eBay - I bought an OBDII to USB interface for £40 I think, it works fine on my brothers BMW with CarSoft.