How do I upgrade the depreciated functions:

getFirstImageURL
getTheme

for 1.4.4.4?

Actaully the notice tells you what to use instead. So in short:

getFirstImageURL:
$firstimage = $albumobject->getImage(); $firstimage->getImageLink();
getTheme is only needed if your theme has different personality to switch css files. This is now done via the css_head filter. See the default theme's functions.php for an example right at the beginning.