If you want to be 110% explosion safe, use a Sawzall w/12" blade and cut while full of water.
Once you have it cut open, if you can still smell the skunking, I'd build a bonfire and roast the pieces - lots of heat should get rid of that oil. (or use one of those million BTU propane torches - they are cheap at Harbor Freight but get the one with the spark ignitor.)
Another thought: I clean out the rust from a gas tank by strapping it to my cement mixer and putting a bucket of p-gravel in it. Did a remarkable job. Strapping a long propane tank might be difficult if it doesn't fit in the mixer bucket.