I recently modified an office hutch I made 10 years ago : 
It became a freestanding bookcase: 
and a credenza. The credenza required no modification, but the upper bookcase portion required a new bottom and base plus a new top to cover the uneven original top surface. Here you will see photos of the original hutch and the bookcase (minus a few of its adjustable shelves) plus detail photos of
the base: 
and the new top: 
The new cherry is obvious in these photos, but over time will darken and should blend in nicely with the patina of the original wood. This lucky lawyer as well as a pile of his partners got to buy (and take home) the custom office furniture I had made for them at pennies on the dollar when the firm decided that uniformity, not individuality should be the decorating theme.