Product review (5 stars): it worked and i fixed it myself.
first of all, you probably do not need a new spring. you need the weird pulley attachment that breaks every 5-6 years.
but if you bought the spring and the pulley, and want to know how to install, go on utube and find the appropriate video.
there were two videos when i looked (in 2013) and you had to watch both of them to get everything figured out.