I'd hit it with 30# of co2 to seal the lid, purge a couple times, hit it again, check for leaks, then purge it almost flat to remove any remaining o2. Leaving a bit of pressure on it won't hurt though. Might actually be better.
When you do carb it up, you will get a bit of sediment in your first pour. After that, if you don't move the keg around, you will be good!