You will have to do an upgrade from 10.04 to 10.10 then to 11.04 then to
11.10 before you can upgrade to 12.04. Your best bet is to do a clean
install.

>
> First, I have some installed applications that I would hope would remain
> untouched. These are Hercules and VirtualBox, where I have Windows Vista
> running. If necessary, I would re-install them, but I read somewhere
> (OMG! Ubuntu, I think) where the blogger intimated that the upgrade left
> such applications intact. If that is true and requires any special
> action or approach, I would love to know that before I start.

With an upgrade I would imagine yes. But I've always done a clean install.

>
> Secondly, I have a separate home partition which I want to keep and I
> understand that there will be an option somewhere in the process that
> permits that. Is this also available in an upgrade as opposed to a clean
> installation and will it be obvious?

Since you have the separate home partition the clean install is the best
bet.
You will have to reinstall Hercules and Virtualbox. So long as your
storing your Virtualbox virual disks on your home partition then it
should return with your old settings.
That is the beauty of a separate home partition, you keep your settings.
Now if your using Wine then you might have to reinstall some of those
programs, but it should persist after reinstall. I've never had a
problem with it either.

>
> I'm a reasonably experienced Ubuntu user with about 2 years use under my
> belt, but this is a new step for me and I would appreciate any
> suggestions or warnings before I start.


To summarize your best bet would be a clean install, otherwise you will
have to do 4 upgrades to get to 12.04.