Happy daze indeed! Congratulations - that's terrific news! It's all hard to take in, but don't be afraid to email your agent with queries. You can save small ones up for one single email. Your agent is not your best friend, but they are the nearest thing you'll have in the book trade.
The agent will send it out to editors who they think will like it and will think it fits their list. The editors will read it, and if they fall in love with it too, they'll then take it to the next acquisitions meeting, where they'll try to persuade (in the teeth of other editors each bearing books
they've fallen in love with) publicity, sales, marketing, production and the rights dept. that your book will make money. If they're all convinced, the editor will then get back to your agent with an offer. Some very senior editors have the power to acquire without anyone else's say-so, but that's increasingly rare. The offer will be 'an advance' - i.e. an advance on the royalties they expect your book to earn. It will be paid, via your agent who deducts commission and passes it on, in three or four chunks - on signature of contract, on delivery of manuscript (often the same), on hardback publication and on paperback publication. Advances are down
a lot in the recession, and publishers are getting more aggressive about wanting a lot of rights (see below) to make up for what they are having to pay. They may offer a two-book contract - which is one reason your agent is encouraging you to get on with it...
If several look like offering your agent will suggest which one is best, or that the book should be auctioned, which is a sealed-bid system. If one publisher loves it but is anxious not to get pulled into an auction they may make a good offer as a 'pre-empt', under which your agent agrees not to offer it to anyone else.
The rights department is in charge of selling the subsidiary rights to your book: e-book, audio, large print, book club and all foreign and translation rights. Your publisher will almost certainly want any contract to include them handling these rights (because then the payments go towards paying off your advance) but if your agent wants to take your book to LBF then it sounds as if s/he is planning to keep at least foreign and translation rights to sell separately. Which, assuming your agent is as good or better as your publisher's rights department at selling them, is good for a number of reasons I won't bore you with right now, not least your cashflow. Rights are often the bargaining chips in the negotiations over the advance, like curtains and carpets in buying and selling a house.
It's all incredibly exciting. On a sour note, I do know that agents are saying that not so long ago they never failed to sell a book. Even top agents can't say that any more, though the best agents won't drop you if the first round doesn't work, but will persevere. It took my agent two years to sell a funny little book about the night time and a curious incident involving a dog...
The other thing I'd suggest is that you join the Society of Authors. They have lots of information, as well as good seminars and some social events, and local groups. For the price of the membership fee they'll check any contract with their legendary legal magnifying glass. Your agent will obviously check contracts that s/he negotiates, but I do suggest that you get the SoA to check your agency contract. Not, I'm sure if s/he's a major one, because there's anything dodgy in it, but because there are always things which have implications you might not be aware of...
http://www.societyofauthors.org/index.html
And whatever happens, enjoy this moment. It's a huge affirmation of your writing to have this happen!
Emma
<Added>As you'll have gathered, it can vary a lot how long it all takes - anything from ten days to much longer, depending on meetings, and who's on leave, and so on...
Once you've signed a contract, it's usually about a year - not often less, sometimes more - from then to publication. There'll be some editing, almost certainly, then a copy-edit, typesetting, proof-reading. Pub date is all about where it fits in the promotion schedules of the big buyers - 3-for-2, Book of the Month, etc. etc. Bound proofs will go out to people like the trade press and the big buyers (Tesco, Asda, Amazon, Waterstones) will be shown it about 6mths before publication, and then Publicity starts gearing up: press releases and review copies and so on perhaps two or three months before.