How much would it cost to customize ...

[Trip]

Depends on the designer and what they dub simple. The ones I have delt with in the past were 40.00/hr. However, in most cases I would think if you were buying a skin from them and needed some alteration(s) they are usually quite reasonable to deal with. As far as what you need, sounds like a simple CSS change, can't see a huge charge for something like that. Of course, like anything it depends how the theme is set up.