I feel the opposite is true. Charest won't have Campbell's initial surge of popularity for being a woman PM, and that will hurt him IMO.
He might not have reached the same initial heights that Campbell did, since there naturally would've been a lot more excitement about her election than there would have been with Charest, but a) she was an awful campaigner and b) Charest was very popular in Quebec, where up until a few weeks before the election the PCs still had a decent hope of winning somewhere around 20 or so seats. Plus, a better overall campaign likely means the party is able to hold onto more seats in places like the Atlantic, Ontario, and
maybe the west (though obviously Campbell would've an advantage over Charest in the region; ironically, though, a better campaign likely means Campbell herself is able to win re-election, likely positioning herself for a run for the leadership once Charest (presumably) resigns.
So overall I think the PCs would do a lot better, but probably not well enough to pass the Bloc Quebecois or Reform (though it is plausible). An outright win really isn't possible unless there are earlier butterflies. If I had to guess I imagine the Liberals win about as many seats as they did IOTL, if not more (with greater vote-splitting between the PCs and the Bloc/Reform likely countering Liberal losses in the East), the Bloc/Reforms in the high-30s or low-40s, and the PCs with around 30+ seats.