You're on the right track- use aluminum foil to cover the electrical stuff (*especially the opti*) and don't blast water on anything that common sense says oughta stay dry. Lemme think, '96 is an LT1/LT4...(have 'em in my 9C1s)...don't get the engine computer too wet (I forget where they are in 'vettes). Remember that if you get the serpentine belt really wet you won't have accessories (including power steering ) until it dries.
Maybe put some soft towels on the fenders/cowl/etc. so you don't get them covered with engine compartment dirt.