Jeff is right on the money. A trouble/work light is cheap insurance and greatly improves your odds. All you gotta do is keep the engine compartment above freezing, 34 or 35 F will keep any water in there as liquid water. The time invested is nothing... Drag an extension cord out, plug in teh light, turn it on, put it in there a, dnclose the hatch.
Whle the block might be drained, there are other places where you might still have some water that could cause an issue. Keep them above freezing and you will be fine.
This is one time to not go with a CFL fluorescent bulb though.....
You need the heat from an incandescent bulb...