Changing Sidebar Widths In 3 Column Neoclassical Theme

I recently redesigned my blog using the 3 column Neoclassical theme. I would like to start adding ads in a 125×125 format, and am considering placing them side by side (2 columns) in the right sidebar.

My question is this, the sidebars are currently set to 190px; would it be worth modifying the code to make the right sidebar wider to accommodate the ads?

My estimation is that the right sidebar would need to be 280px, leaving the right sidebar at 100px. I’ve been mocking up a page in Illustrator and it looks pretty narrow.

Also, I am concerned that modifying the sidebars will screw up the theme headings like “navigation” and “search.”

I am new to this, so I’d love any input. Should I change themes all-together if this is my goal?

Thanks much ??

Penny
https://www.pennyplastic.com