Do I need to resize them or are the pictures already the correct size for printing straight up?

You can print this PDF I made at 100% on 8.5 by 11" paper.

https://dl.dropboxusercontent.com/u/1355055/IA%20December%20Erata%20%2B%20Smuggler.pdf

You would have to do that. Here is the link to the word doc file on board game geek. They are already sized for putting on top of the original card.

https://boardgamegeek.com/filepage/126289/new-skirmish-changes-printable-card-updates

Thanks, the boardgamegeek one worked great.