Permalink Help….I messed up

I made a huge error and really need help. After searching and reading, it seems this can be handled but I got confused by reading to much maybe. Why I made this change prior to knowing, i;d rather not discuss, all the you should have you should not have’s. I would rather just learn and move on.

I had the bright idea of changing my sites permalink structure after years. Not thinking anything would happen. Low and behold I was faced with many 404 errors(about 800) in google webmaster tools, and my site is losing rank as well over the past few weeks.
I did stay adding content during the whole time doing all this and having others linking to the content, so will im going to quess those newly created pages are now not found(in bound link) because I changed it back.

I read something that You can edit the .htacess file or something.
I changed my link structure back to what it was after a few weeks of noticing all the errors and continue with 404 errors and google bot cannot access server due to this amount of errors.

At this point, what should I do. Something with this .htacess file, just wait and see what happens, can I have a 404 page that redirects back to home page or something?

I did stay adding content during the whole time doing all this and having others linking to the content, so im going to quess those newly created pages are now not found because I changed it back.