Be prepared to do a fair amount of reading, and a good amount of work: this is not a simple subject in the slightest, and your entire system design will be involved, from teh basic database design on up.
Start reading here:
MSDN: SQL Server Replication[
^] - but you will probably want to do a search on teh subject and read upo a fair amount before committing yourself to a design. This is not something you want to add retrospectively!