Yes, I had version 8 and 8.5 was offered as a download only version which required 8 to be installed.   I understand the DVD version was able to be installed clean.
 
Strange but true.

Actually it made a lot of sense at the time. Wasn't 8.5 the first upgrade available as a download? I think they were scrambling for a way to provide a d/l solution for the bandwidth challenged.

mixmkr

...I'm guessing I would be giving them access to my Cakewalk account to allow them to download the upgrade and the time involved to download, install and make sure it's all running.

Downloading and installing are separate processes and don't necessarily need to be done on the same PC.  You could download the files yourself and pass them on to the computer guy.  He does not need to log in to your cakewalk account to install the software.
 
Also, you don't need to have the software installed to qualify for upgrades, as long as you have it registered in your Cakewalk user account.  It's the fact of being a registered user that qualifies you for Cakewalk's offers.
 
Or maybe I've misunderstood.  Forgive me if I am stating the obvious.

When I had my new DAW built fro me, the vendor asked me if I wanted them to install my software for me.

I said yes please, just to avoid sitting there for hours putting disc after disc into the machine.

BUT - in order to do that, I had to send them my discs.

I think they charged me an extra £10 on top of the DAW cost, so I was happy for them to do it.

Jonbouy you are right on the 8/8.5.3 for my installation that required an older version to be installed.