I have a few questions pertaining to chains and my conversion overall from single speed to "multi" speed.

1) I have Shimano 105 9 speed 5501 shifters. It came from a triple setup, but I was wondering if this shifter is double compatible w/o me accidentally shifting to a ring that's nonexistent.

2) For a triple setup, how many link chain should I be looking for? What about a double setup?

3) Has anyone tried different chains and noticed a big difference between the chains? There are some Dura Ace chains at my LBS for about $50, and then there are "generic" Shimano 9 speed chains for just $18. Please also recommend any other 9 speed chains of decent quality/price.

4) How much does cable and housing cost for a conversion like this?

5) Is it difficult to put everything together on my own? Or is it recommended that I bring everything to an LBS to set it up?