Yes, I'm guessing by about 20-25%.

The crust will be a bit thinner as the same amount of dough needs to be spread out over a larger surface area, but since it is not a dough that you have to roll out, the handling shouldn't be particularly tricky. You might consider not filling the pie tin with the crust covering the lip or compensating by using more whipped cream to hide the gap.

Finally, it may bake faster; I'd start checking at the 10 minute mark.

Good luck.

I'd say the difference would be larger, not far from half again as big (you can't calculate exactly because of the shape)- you really need to adjust the recipe

An 8" pie pan holds about 4 cups liquid. A 9" holds 5 cups. The .5 additional inch of yours increases the volume even a little more.

If I were you, I'd go buy an 8". If you don't increase the recipe, the pie filling will be very thin. If you do increase it, it will be awkward because of the can of evaporated milk. You could increase it by 25% if you don't mind a leftover partial can of evaporated milk.

You could make Thai iced tea with the leftover milk.