I've done a few of those RHEL/CentOS/Ubuntu moves myself, and even though it was a pain I'm still somewhat impressed over how painless the actual move was when I had good documentation and also still terrified of what it feels like to try to transition undocumented boxes.
I dislike windows and the M$ ecosystem but as far as server management for undocumented servers it's much easier to deal with them than for Linux stuff. For an undocumented Windows server, you send out an email, wait 2 weeks, shut it down and listen for the screams.
For an undocumented Linux server, you send out an email, wait 2 weeks, prep the fire extinguishers, batten the hatches, and wait for the mob of angry villagers to storm the DC with pitchforks because thanks to you their print server for their paper checks is now printing in Klingon and it can't be fixed without resurrecting the guy that wrote the software 6 days before he died of terminal terminal disease.