Thumbnails in gallery questions

Ok, I have been through the tutorials on Kirupa about XML galleries and adding thumbnails to those galleries. And I understand all of it. However, I am trying to create a gallery and I have a couple questions.

I want to have the main picture on the left side and the thumbnails on the right ,vertically, not horizontally. I can figure that out but, I want two columns of thumbnails (6 rows; 12 total thumbs) and the spacing between each (top to bottom, and left to right) to be 10 pixels. Can anyone help me with this?

Also, insted of scrolling based on mouse position. I want to have two buttons, one on top and one on bottom, that when clicked scroll the thumbnails. When the thumbnails scroll I want an entire new set (6 new rows) to show up. Can anybody help with this?

Thanks in advance for the help.