I've "returned" a number of times...mostly after long breaks.
If you go to the Everquest website, I believe, there is a link to purchase the game. You can purchase a package which will include all upto and including the most recent expansion. I believe it is about 39.99.
For what it's worth...SOE is about to release another expansion in about three weeks or so. If you purchased today, you would have to repurchase the expansion (should you desire it) later. If you waited until the release came out, you would be up to date. No suggestions on what you should do here.
Servers, don't know. I've been on the Rathe since 2001. It has been through multiple mergers. Most recently about three months ago. Population is reasonable. Might go to the Everquest discussion forums site for more guidance there.
Good fortunes, good hunting.
Kraayt