Screen & lid cover separated

There is a few different issues at play here. If you had the screen cover glass replaced I've seen a few bounce back as the adhesive really needs to be cleaned off fully and replaced instead of re-heating as some have done.

The lid frame is two parts sometimes the outer shell gets a bang which snaps the screws/glue between them.

We still have quite a few of these in use for our field staff. They are workhorses! But, like laptops of their time frame they have their limits. I often find people outstretch what these systems were designed to do. Apple never intended them to be desktop replacements (just like all of the other manufactures). Laptop systems in general are for road warriors, not gamers. Yes, you can still do many games but most of the newest are just too hard graphically for these older systems.

OK, what to do here?

You'll need to pop off the cover glass and you may need to pop out the LCD so you can re-anchor the mid frame back to the outside lid. As for the cover glass you'll need to carefully clean off the old glue and then use some hot glue to re-apply it (or you can use some double stick adhesive strips).

Here is an IFIXIT guide: MacBook Pro 13" Unibody Mid 2009 Front Display Glass Replacement to walk you though the process to pull the cover glass off. Do be careful with the heat gun as you can melt the rubber gasket quite easily. Hopefully all you then need to do here is clean it up and re-attach it. If you need to dig deeper let us know.