Two-way replication between SQL Server 2005 and SQL Server 2008
From your comment update, it sounds like Merge replication could work well for you, mostly due to the minimal updates. It's a lot simpler to set up and manage than two-way transactional (which is what the scary link I mentioned deals with--I should have left that for later).

In a nutshell: https://blogs.technet.microsoft.com/meamcs/2011/01/06/merge-replication-step-by-step/