Suite 3.7.4 > 4.0.3 It's not gonna be pretty is it?
 

Okay so really I was hoping for some help/advice on how to undertake what sounds like a possible messy process. On my end it sounds like from what I have read is go about it in this way:

First do a full backup and then disable any plugins
Install 3.8.4
Then install 4.0.3
Sounds fairly simple however we'll see how smooth that all comes to be. Is there anything I am missing here or did I not quite understand the steps? What to be aware of from your past experiences, if any.

This is the part I am also struggling with. I have a license that I bought for another site which I now am no longer pursing. Again this is the one with the license.

I want to use my license or valid version of 4.0 on my other site which the license has since expired. This is the one I want to upgrade from 3.7.4 > 4.0.3. Can I do this? Btw both sites are under same account as well, not sure it that is important or not to mention.