Like many other of the gentlemen on this post, I too was a LEO. After over 25 years on the job in NY, and many seasons as a firearms instructor, I can tell you that the advice you have gotten here is great advice.
I happen to have a 3 inch 66 like the one you are talking about. It was a special run made for a distributor in 1985 and in fact only 2500 were made.
That particular gun is as accurate as any "Smith" I ever carried even with longer barrels. It's a great choice and a steal at the price you paid for it. Your dealer is right, it has some collector interest and a research on the Smith and Wesson Forum of this gun will answer many questions regarding this gun.
I caution you on it's use as a primary weapon for law enforcement however. After reading the other responses I hope you are getting the impression that familiarity and practice are paramount with this weapon, as it should be with any firearm actually, but there are probably better choices out there for extended LEO use.
If you are forced to purchase your own handgun then in all practicality, please get the best gun you can get for the money. Preferably new! There are a lot of "tools" in the trade of Law Enforcement..not all of them are inanimate objects, but the one inatimate object you need to feel most comfortable with, in terms of reliability, familiarity, and personal protection, is your sidearm. Please dont settle in this regard.
Try to find out from the firearm instructor in your agency what his opinions are, he will know the rules and regulations for firearm use which should include specifics such as type of gun and caliber and possibly specific cartridges, and then purchase a new firearm accordingly.
In the meantime, keep the 66..shoot it and enjoy it, and most of all, be careful and accept our prayers that you will never have to use it or any other gun as a LEO.