City-20 Questions -Category Images and Upgrade Question

[webone]

Hi, I have 2 questions on the City-20 theme.

1. I have changed the archive.php to show the excerpt instead of the full post, but I would like to display the thumbnails on the category pages as well. I saw this post re: the Lifestyle theme and tried the code mentioned here in this thread, but when I tried in on the City-20 theme, I got blank category pages. Could someone please tell me how to get images to display ie: what code to add in the archive.php for the City theme?

http://www.studiopress.com/support/s...php+thumbnails

2. What is necessary in order to upgrade to the most recent wordpress update if using the city theme. I read that some people were not able to do the upgrade and so are there any special preparations that I need to do in order to continue to use City with the latest Wp update?

Thanks so much for the help