My TD5 Defender wouldn't start, quick search revealed oil in ECU.

I'm going to have it towed to a specialist Landy garage for repair. Two questions,

1. Any idea roughly how much this repair is likely to cost?
2. Any suggestions for making sure it doesn't happen again?

Thanks

The injector harness will need replacing, this should cost around £100 - £150 pound if a garage carries out the work or around £30 if you do it yourself, if it is an official Land-rover dealership think telephone numbers. The new injector harnesses are uprated so should not leak past again.
You may be lucky with the ECU if it only needs cleaning.

Scooby 22, that's very useful information. Thank you!