How to sell built Lego sets?
If the sets are indeed complete with all parts, minifigs, instructions and even boxes then I'd recommend Bricklink, as the collector community there would be more appreciative of these features. Whereas on Ebay and Craigslist you'd find more people who just want a playset and couldn't even tell if a set was complete or not.

For higher value sets (like yours) and for the european market I'd give Catawiki a look as well, as their reviewer and escrow system helps avoid scams and other pitfalls - for a higher fee for both buyers and sellers.

For price suggestions check these links below:

Slave I
Sandcrawler
TIE Fighter
Snowspeeder