Yes you have and the worth depends on your technical expertise.
http://www.ifixit.com has guides with photos, maybe they can help you making a decision.
It took me less than an hour to replace the HDD in my 2007 Aluminium iMac and it was quite easy, easier than I anticipated, but I built several PCs in the 90s, thus I might have had that advantage.
i can't find a very good video about it... do you still need to use the suction cups to remove the screen or there is an easier way?? Thanks
Still have to use it