Furniture, Wood and Cabinetry Finishing - Best tool to cut ends off long cabinet top?

I bought a painted cabinet to fit between two built-in bookcases and need to reduce the top's overhang by 3/8" on each end in order to slide it into the fixed space. I'd like to use a hand tool will enable me to make an accurate, square cut on the first try. The only saw that I own is an 8" circular saw - and past experience with cutting boards doesn't give me much confidence that it's the best tool for this job. Thanks - JS

That will give good results, properly used. Use a fine tooth carbide blade, cut from the back side(cutting on the top can result in tearouts/rough cuts), and clamp a straight edge as a guide for the saw.