Can he change more than 1 die? Seems pretty expensive if not. I have more questions but I'll start here.

No. Just one die in one of your roll's each round.

Its a super powerful ability for ships where that 1 Die can count for EVERYTHING, mainly high risk/reward lists where you have super deadly but super squishy pilots (Like Soontir Fel) who may die if they get just one below average roll. Palp-aces (An assortment of 2 aces + Palpatine in a Shuttle) are the dominant meta list.

Extra: The Gozanti pack "Wampa" Tie fighter pilot has a combo effect with Palpatine, making him a popular 4th ship to round out some Pal-Aces lists.

P.S. Probably the wrong place for this question.

It's actually the best place for this question because this is the Rules Sub-forum and Upgrade cards are extensions of the rules. The answer is on the card: "Once per round, you may change a friendly ship's die result to any other die result." A "die" is singular meaning one, and it's only once per round. But it's not restricted to just combat results. It could also be used to negate the effects of an asteroid or debris cloud if a ship hits them, a damage card that requires a die roll, or any upgrade that requires a roll for something.

It's actually the best place for this question because this is the Rules Sub-forum

No it isn't. This is the painting and modelling sub forum.

It's actually the best place for this question because this is the Rules Sub-forum

No it isn't. This is the painting and modelling sub forum.

Ha ha. Just goes to show how often I look at where I am.