Hey Jordoss, I have a couple of these myself, and depending on what series you have, I believe the sets go for anywhere between $20 - $200, depending on the buyer and seller. I was able to find the orange set on eBay, it's going for like $30 + $10 shipping. I have the blue set (most of it anyway) so I'm curious to see how much you sell yours for.
Also, do you have the "well-endowed" version of the C3PO card? I think if you have that one, the original, the set is worth more.http://www.ebay.com/itm/TOPPS-STAR-WARS-1977-ORANGE-COMPLETE-SET-66-CARDS-/190556936386?pt=LH_DefaultDomain_0&hash=item2c5e1418c2