Wordpress update errors
===

I just went to update one of my wordpress sites. It was my first time updating a wordpress site. 

When i went to update the update screen hung for 20 minutes saying "installing". The website home page was still displaying the maintenance notification. I looked this up and the consensus seemed to be to ftp to the site and delete the "maintenance" file. I did this and now the homepage displays: 

`Fatal error: Call to undefined function get_front_page_template()......`

When i went to mysite/wp-admin it said, "wordpress has been installed, you now need to update your databases". So i pressed the "Update Databases" button upon which i'm presented with the error:

`Fatal error: Class 'WP_Theme' not found in.....`

I have a feeling i've done something very stupid. Can anyone help me out?