Re: Newbie post: What the hell is the difference between neck and bridge pickups?
Depending on the model, you'll also need to check the pole spacing. Some bridge pickups are spaced wider than the neck pickups to accomodate the extra distance of the saddles. Place a piece a paper over the pickup, and lightly circle each pole, and then place that template underneath your strings and see where it matches up.
If you know the maker and model of the pickup, you might be able to match up the resistance of the pickup with what's listed for it, but more than likely, you'll want to contact the manufacturer with the serial no. listed and see if they can help you.
Other than that, it's not going to cause any damage to your guitar or sound if you use a bridge pickup in the neck slot. Like I said, biggest thing would be to make sure the poles match up with your string spacing.