Here you go:
http://fish.shimano.com/content/dam/shimanoweb/fish/sac-fish/en/techdocs/current-models--2-1/STELLA/STL6000FA
http://www.ereplacementparts.com/shimano-stl6000fa-stella-spinning-reel-parts-c-200301_200302_200742.html
You'll have to look for the individual parts that needs to be replaced. I can't tell from your photo what exactly you need to replace.