I am running dirXML with two driver set objects and engines (one in each
of two org containers) and each one talks with one of two AD domain

Can I upgrade one of those to IDM 3.01, and then do the other one the
following month?

Then, after those are done, can I add the secondary tree for the identity
vault as a third piece to that project?

I have to make sure that our current eDir/AD user and password sync is
uninterrupted during this process, so I'm trying to pace it out.