How to upgrade in place from 16.10 unity to 17.04 gnome

[Brian Burch]

There is a lot of historical advice on this subject relating to earlier 
versions of ubuntu, but a lot of it is out of date.

I have switched my own systems from unity to gnome in the past, but gave 
up a few releases ago because unity had improved to the point where 
living with it was better than the pain of switching desktop.

I suspect there will be quite a few users who find themselves in a 
similar situation to me, so perhaps we could start with a nice clean slate?

As background, I did a clean install of ubuntu 64-bit desktop 16.10 onto 
a separate partition and kept my working 32-bit 16.04 LTS system. Just 
creating the spare partition on my all-raid LVM system took a lot of 
time and care. Then, once I had the new system working, it took a huge 
amount of time and messing about to install and configure all my 
applications in their 64-bit versions. Eventually, I had something I 
could work with, so I deleted and re-absorbed the "spare" partition. I 
definitely don't want to go through that sort of process again to 
install ubuntu gnome 17.04!

In "the old days" it was enough to install the gnome-desktop 
meta-package and select gnome from the login panel. As time went by, 
things got more complicated, but I don't need to repeat all that history.

I was quite sorry to read Mark Shuttleworth's interview about the future 
demise of unity - it was a worthy ambition. However, I was very pleased 
to read the announcement:-

https://ubuntugnome.org/ubuntu-gnome-17-04-released/

It seems I could simply be patient and my desktop will be automatically 
upgraded (along with everyone else) in year from now. However, I would 
like to circumvent a few annoying unity bugs and upgrade 17.04 in place.

Is it as simple as changing /etc/apt/sources.list to point to a new 
repository, "apt-get update/upgrade" and then "do-release-upgrade". 
Would that remove unity and install gnome properly?

I would be very grateful for advice that applies to my current situation.

Thanks for being there!

Brian