"Any input on the how dangerous is it for two people with no experience to take off on a boat?" Perfectly safe--as long as you're not one of them.
You might find the frustration decreased, and fun increased, by taking a "basic sailing" course with an ASA accredited sailing school. Books just don't work for sailing, there's too much visceral feel and hands-on that can't be explained in them. Learning how to do it right--rather than getting it wrong and having to unlearn things--will be worth it.
About the boats: I know Louisiana is different from the rest of the US (literally, because it follows Napoleanic Code) but anything with an engine and/or registration number on it may be TITLED PROPERTY. And that's never just abandoned, even when it is abandoned. That means anything you do to or with it can be theft--unless you legally get the title.
Odds are they were abandoned for one of two reasons: People who left town and never looked back, and people who think the damage will cost more to repair than the boat is worth. On many old boats the engine (even an outboard) can be worth more than the boat. So, you need to find out locally what the law is on titles and boats. The marina can probably apply for a "garage lien" or similar, asking for title to be assigned to them because the monthly fees have not been paid and the owner cannot be found. Then, they can transfer the title to you. But without legal title---if you go to register that boat, you may have a problem. If the owner shows up after you put $3000 into the boat, you can lose it all.
Fixing a sailboat can be more expensive than it looks. If the fiberglass has blisters (underwater), if the structural plywood inside has rotted, if the electrical wiring has rotted, if it needs any rigging or lifeline stanchions...you may be surprised at how fast the surprises can add up.
You might find a bargain--but look into these things (especially title and registration down there) carefully. Sometimes a boat is abandoned simply because it would cost more to dispose of the hull (which is classed as hazmat because of the toxic bottom paint) than to buy a new boat.