There is a plugin for thumbnails called thumbnail-for-excerpts/, it might be what you need.
To be abe to use slideshow on nextgen you must install imagerotator.swf. Then you must point nextgen to the location of that file using: Gallery-Options and then on the right side of the page Slideshow.
The usual place for the </body> tag is in footer.php. You can get to that file by going to Appearance-Editor and then in the right-pane select footer.php. Note: If you select another theme, you will have a new footer, as the file footer.php is located in your theme, so your tracking software will stop working, until you add the code block again.
