I would say you can, but I don't know you. What I would suggest you do is download the latest version of Cube Cart, it's free, unzip it on your local computer and look at the actual files to see for yourself if it looks like it will be doable with your own experience level.
It would take you less time to look for yourself than what its taken you to reply here.
The directories you'd probably be interested in once you unzip the files are in the following path...
\CubeCart_3.0.15\upload\skins\Classic\
or
\CubeCart_3.0.15\upload\skins\Legend\
or
\CubeCart_3.0.15\upload\skins\Killer\
These are the directories which contain the different options for the default look and feel of the install, the html and css stuff. Your also in luck, some of the more experienced developers have just started a new message board like this one just for customizing like you are asking about. It's something not officialy supported here just like your new car wouldn't be if you chopped the top off of it and wanted to remove all the doors for a breezy ride.
Now is actually the perfect time to head over there and post questions since they just opened the site like yesterday and it's currently full of experienced developers sitting around over there with nothing to do because not very many people know they are even there yet.
*Edit by moderator/admin. Promotion of 3rd party removed. 3rd party forums can be found
here*
Over the next few days I think a couple more simular sites will be poping up, but the link above as far as I know is the only one actually open and in use at the time of this writting.