Countdown to "XX"th Post?

[BabyU]

I'm nearing 100,000 posts and wanted to hold a contest with a prize for the person that posted #100,000. I would like to do 2 things.

First, I'd like a 'countdown' of sorts on the main forum page that shows how many posts are left until we reach 100k. I have the feeling this is fairly simple, but it's just not registering with me.

Then I'd also like to list out maybe the last 50 posts and who they were made by so that it would tell us who made the 100,000th post. How difficult would this be?

I thought that I could just go into the database and pull out the post with ID #100,000 but the more I think about it, this probably won't work, will it? The database doesn't reuse deleted posts IDs, which means that the post with ID 100,000 isn't really the 100,000th post -- or is it?

I'd appreciate any suggestions or advice. Thanks!