What you would need to do is remove the album art viewport completely (or comment it out), and then expand the metadata viewport(s) horizontally to fill the recovered space.
It is likely that the theme has conditional cases for when album art is present, and absent, so a full width metadata viewport may well already be present. In which case it would be as simple as removing the conditional statement that covers album art and metadata display, removing the "album art present" aligned viewport, and changing the "album art absent" aligned viewport from being dynamically displayed to being statically displayed.
The manual has a
theme section which should aid you in this task.
if you get stuck, or try and honestly feel it is above your head, you could let me know which theme it is you are working with and I could make the appropriate changes myself and give you a pastebin link with the edited content as I did for another user just moments ago.
However, I am generally not a fan of doing this as I'm more of a "teach a man to fish" kinda guy, as opposed to a "give a man a fish" kinda guy (second time I've used that metaphore in 3 days, ...heh).
That's not to say I won't do it, though, as it is apparent that you have tried to pursue this goal yourself - which is admirable - and that is the same reason I made the changes for the other user. I just want to know that people have tried first.

Another option is to look through the
themes section for your device and see if there is already a theme that meets your needs.
Let me know how you get on.
[Saint]