You're probably OK. That plug likely burst when the system started getting some pressure. If you drained the whole system, the puddle would be much larger than a 1x2 puddle.
What EFI system are you planning on using? I"m using MS3X full sequential. I don't have any miles on the car yet but I've started it a few times and messed with the idle configuration. It seems pretty easy so far. I do like how easy it starts when cold.
