You can rename the projects in Visual Studio, and it'll fix up a lot of stuff for you. It won't, however, fix the folder names. Here's what I do when renaming a project.
1) Remove the project from the solution.
2) Rename the folder the project is in.
3) Re-add the project to the solution.
4) Rename the project in Visual Studio.
This will leave behind some items, like dlls with the old name in the bin folders.
Now, for the TFS problem. I think when you add the projects back into the solution they will want to create new entries in TFS. This probably isn't what you want. I don't have a TFS available to me in order to test this right now, so I might have this part wrong, but I think if you were to update the "working folder" for a project between steps 2 and 3 it might hook it back up correctly. Try this with a small sample solution before doing it with anything terribly important.