I'm repeating some of the info above:
Do you have a P-01, or a Compact?
If its 9mm, its a P-01. It shouldn't be that much heavier (if at all.)
If the new gun is a .40, its a 75B Compact -- as they don't make a .40 version of the P-01 yet.
The Compact in .40 comes with a steel frame, and that would make it noticeably heavier. The .40 Compact has the same frame design as the P-01, but has a safety rather than the P-01's decocker. The steel frame makes recoil a bit more manageable, too -- so the weight is offset a little by better shootability. If you don't plan to carry everyday, its a non-issue.
Either way, in terms of value -- you came out ahead -- if you ever want to sell.