There's a few things to check out here. Firstly, is this a facelift X5, with xDrive etc.? What build month in 2003?
What about the state of the battery? Fully charged and working well?
Did the alternator get soaked with oil, while it was running? The oil filter housing is directly above the alternator, so it likely got dumped on, which can damage it...
When you say it won't kick over, do you mean the starter motor cannot turn the engine over or that it turns over but won't fire?
There a number of electrical systems on the left side of the engine that could have been compromised by the errant oil (including the engine temp sensor), so an idea of how extensive the oil spread was might be helpful, along with the steps you've taken to clean it all up. For example, if you unplugged a lot of wiring looms etc. then some of your issues might be related to your clean up efforts rather than the original fault.
