Apology accepted. The reason for thumbnails not being shown is simple. In functions.php remove function keyword from lines added. These are function calls not function definitions. In home.php the proper placement for call to display thumbnails is just before the_excerpt so it should read:
<?php if ( has_post_thumbnail() ) the_post_thumbnail();
And, of course, remove what you've added to division "sliderContent". There are more places to display thumbnails ( single.php, page.php, etc ).
If you feel you can trust me, give me admin access to your website or FTP access to it, and I can fix it for you in 5 minutes flat. I you decide to do it, send these credentials through the contact form on my site: Contact. If you are not comfortable with giving me access, send these two files: functions.php and home.php zipped, using contact form mentioned above and I'll send them back to you, corrected.