Oil puddles on top of the engine only mean the LIM bolts weren't sealed when they were put in or the valve covers are leaking badly after the head gasket job. Not a huge issue either way.
Sitting two years huh? Toss a battery in it and try to fire it up. Get a video of it when you do. Then post that up. We can tell you a lot from a little info, but as it sits now..it's mostly guessing.
There is no way to loosen a tensioner to have the belt slip off. So rule that out and put the belt back on. If you have questions of where connectors go..get pics and we'll tell you what needs to be done.
One note.. do not rev the engine high or take it out and beat on it at all. Two year old gas will probably fire up the motor, but super unleaded is an absolute must in a supercharged 3800. Also ask her what fuel she was running....before you tell her super is required.
