Its awhile since I sold my Savage...I had a 1986 model.%26amp; as far as I can remember......all you do is pull off plug lead %26amp; use a long sparkplug socket...or a plug spanner %26amp; extension bar from a socket set...
you could have a look here...might be able to find a download with some info in it...
http://www.dansmc.com/shopmanual2.htm
dont think you have to remove the seat...but if you do there was two screws on the back edge of the seat..
this lets you remove the seat so you can get at the bolts that hold the tank on...
found a site that has downloads of micro fiche...
its in german but the pics look pretty good...Diagram of seat removal on page 55 ...
http://www.ls-650.de/html/downloads.html