3
Yeah, $25 will buy you about 15~30 minutes worth of time from an experienced developer. Intergrating your basic design into XOOPS wouldn't take too much longer than that, but by the looks you'll be after a custom template set as well which would be more work than $25 would get you. Just something to consider.
*Edit*
Not meaning to discourage you, just trying to give you an idea of what to realistically expect for you dollar. As stated, $25 *might* get your basic theme implemented, but it would not get you templates as well.