Now, I don't really know the firepower of the Klingon fleet, but an imperial fleet of Star Destroyers would make a very hard punch. Plus, if you think about the support ships, Victory-class destroyers, Nebulon B-frigates, Tartan patrol cruisers, accelrator cruisers, and the early Reublic assault cruiser and a lot of other types, that only adds to the firepower. And don't forget the thounsands, and thounsands of TIE fighters.
So for me, it dosen't seem like the Klingons would have much of a chance, unless they've got heavey firepower and shielding.