Seriously now... Are you asking as a general scenario, or is there a specific case you are involved with? If you want help unloading a 'sizeable fortune', what's in it for me? Not that I'm greedy-- but professional assistance comes with a price-- partly because of the legal and liability issues that can potentially affect those involved.
The very first step is to document a history of the actual finding of the site and the fortune, and the nature of the fortune. Is it all in bars? How much does each one weigh? How pure are they? How easy to transport the whole amount, or can it only be transported a little at a time? How secure is the secrecy of the location, and what is the likelyhood that someone else will 'stumble' on it? Can you document that you found it legitimately on land you have legal access to? Is this located in the United States or its protectorates, or is it in a foreign country? Under what country was the metal originally mined, if different? Did you really recover it or do you just hope to locate something in an area where you're 'just sure it's here SOMEwhere'?
The second step would be preservation. If the bars are of a historical nature, the value is more from the form than the bullion. Ie: if the bars can be traced to a certain assayer in California who produced them in, say, 1852 and went out of business 3 years later, a 20-oz bar with a bullion value of $8000 might in fact be worth $25000 as a specimen. In that case you would want to take every precaution to prevent any defacement damage which would decrease its value dramatically.
The third step should be thorough documentation. Photographs, maps, and any papers that prove you found it legally, or with permission.
Beyond that, you can start to research the laws, consult with lawyers regarding potential applicable taxes (local and national), and so on. (Yes, the IRS will want a cut.) You would want to find how the 'fortune' came to be where it is, in case there might be legal claimants. You want to know everyone who might hold a legal right to the treasure, including insurance companies that might have insured it before it was lost or stolen (if that was the case). If you try to hide it from legal claimants you could set yourself up for a lot of trouble-- including prison time.
That's about as specific as I can get with the information you've supplied. I hope it helps. (If you seriously need some professional assistance, you can send me a private message-- if you proceed anything you do will be confidential.)
The trouble with a large fortune is that even if you did everything legally, it will (by its very nature) incur lots of problems. Better to start off looking for a small one!
Sleep well!