Would getting an associate's degree be the right course for someone who already has a B.S. in an unrelated field?
This would depend on your overall goals. Do you want to be hands on technical, write programs/code/applications and are you looking to move in to management?
As mentioned in previous post Associates in IT typically come in two flavors, one for the highly technical minded that are a)looking to be in the trenches and b) seeking quicker employment. The second flavor is for those looking to move in to Information Systems Managment, looking to specialize in programming or looking to offset the cost of a four year degree by taking their pre-reqs in a two year school first.
I have found most colleges will accept/transfer credits for courses going back about 10 years for your math/english/humanities etc. classes and about 5 years for advanced science classes. College algebra is college algebra, English composition is still English composition. I would speak with a local college counselor and see how much of your current B.S. you can apply to a 4 year CIS/CS(tend to be B.S.) or MIS (tends to be B.A.)degree. Why repeat classes you have already taken and payed for in the past?