Very basic SRM-MDM install prep questions

I can't seem to find the magic combination of clicks to get me to this information, but I believe I've see it out there somewhere. Most of the documentation I can find is aimed at the business users, not the technical (BASIS) side. I'm hoping someone can help me.

I've been told by my business folks that they want to use SRM-MDM with our current SRM 4.0 system. I'm trying to find out the prerequisites to give them an estimate of the work involved. Forgive me, because I really am starting from square one with the SRM stuff.

From what I understand, unless we upgrade to SRM 5.0, we will need to use SRM-MDM 2.0. Looking at the install for that, it appears we need to first install a MDM 5.5 system, then install the 'add on' for SRM-MDM. Is that correct so far?

Now for a couple of other questions. Is XI required in this example above? SRM-MDM is only going to talk to SRM 4.0. Can this be done through RFCs? If so, this is when we get into versions for the plug in.

I'm sorry if this is very basic. I'm just trying to make sure I don't mess up some of the foundation assumptions before I get too far into it. I also don't want to estimate 40 hours, if it's going to take 200.

Thanks in advance....