You would be better off trading your F3 for an F100! The F80 (or N80 as it is known here in the U.S.A) is a good camera but not as rugged as the F3. As others have mentioned you can get an N80 for a reasonable price; much less than the price of a used F3.
I have an N80 (as well as an F100, F3HP, F2, F, etc.) and I think it is a very good camera in terms of accuracy, weight, ergonomics, and size. I am not too thrilled with the somewhat loud autofocus though. Also, the batteries are expensive compared to the 1.5 button-type batteries of the F3 or the AA size batteries of the F100. I have the optional battery grip for my N80 which lets the camera operate with AA size batteries, but the camera is bulkier.