Before I start cutting my keg: depressurized?

[bcubed]

Bought the keg from an aquaintance. For safety's sake, hooked up a tap to it and opened the spout. No air or beer came out, so is it safe to consider it depressurized? (Pretty sure it is, but I'd hate a nasty surprise).

Also, for heating: The edges of the keg curl over and keep the center suspended above the ground (or a hot plate, in use). I could cut off the edge completely, but that would leave a round bottom, which doesn't sound safe. Does this mean I must use gas heat?

Finally, the coil. The design I'm going to use passes the coolant through the vapor (rather than the other way around), inside a 3" copper pipe. This requires a tight coil for the coolant line. My source says that bending it around a 2" pipe, using a sleeve, will prevent kinks; when I looked into homebuilding aircraft, they reccomended filling a fuel line with sand ahead of time if a tight bend was needed to prevent pinching off the line. Will the sleeve be sufficient?

The last two might be already answered, but I was concerned about the safety aspect of a pressurized keg, and a search came up empty.