I would suggest you to jot down the upgrade path first, I don't think Product Upgrade Advisor would help you much as the upgrade path is pretty big
You might need the link later, once a couple of modules have been upgraded
To start with refer to the good old compatibility chart
Check for the upgrade path, raise a case with SolarWinds as well.
I would have quoted 2 to 3 hours per module upgrade but the main challenge in your environment is -> "how would test if product is working as expected without any issues post each major version upgrade" as lot of things have changed over a period of time between versions.
Hope it helps
Thank you for your help.