I have made a great deal of progress! The Ubuntu guest is up and running beautifully with guest additions installed. I am replying to my own post with cautious optimism because I'm not entirely certain that I can delineate each step with certainty to be helpful to others. This tutorial was helpful http://www.psychocats.net/ubuntu/virtualbox even though I am still running the Win7 RC. The only difference for me was that once the guest was installed the only option was to restart, not continue, which I did. I initially got the garbled screen resolution again. This is where it gets a little fuzzy because I did two things( with guest running or not I'm uncertain): In the VB machine settings I bumped up the amount of video memory to the full amount because it was set to something ridiculously low, and removed the .iso under the "storage" section of the VB settings. When you do this you get a message saying you won't able to install the GA's but you have to do that or each time you start your guest it will try to boot from the image rather the OS you just installed. In retrospect that makes perfect sense, but remember, this is my first rodeo. Amazingly the guest loaded properly, I allowed the Ubuntu update manager to get and install updates(this stalled for few quite a few moments and I nearly aborted.)
At this point I restarted the guest and VB itself which brought me to the point where I had a functioning guest but with the restrictions you would imagine without the GA's. The How To on this board for installing the guest additions for Linux got me the rest of the way.
I did not need to add anything through a terminal ( the Ubuntu release ready out-of-the box?) With the guest not running, I re-attached the .iso and then highlighted the GA, 30-something megs, started the guest and it was automatically mounted on the ubuntu desktop. Again, this part is unclear as I tried numerous things: I double-clicked the icon which opened the guest file browser. In that folder there are numerous files/folders. I finally tried( clicked) the one labeled Linux guest additions .sh(?)and chose run in terminal. I restarted everything and it is working!!
I apologize the the lack of detailed steps. I wanted the others who are struggling to know that this is do-able. I need to install a retail copy of Windows before the weekend is up, at which time I will recreate this machine noting exactly the steps I'm taking.