Flash for complete idiots - need help

For my entire photographic career, I have essentially ignored flash. Either I was shooting landscapes, or I didn't want flash to bug my subject, or I preferred to shoot in natural light, or....

In any event. I know virtually nothing about flash and how to use it. I have noticed, however, that I have been increasingly shooting in situations where a flash might be useful - such as a recent office staff picture, or at conferences or briefings.

I would therefore like to purchase a flash unit and learn. I try to read threads about the various advantages and disadvantaged of the various flash units, but after a few seconds I start to get confused and drool. Apparently I am a learn-by-doing-kind-of-person.

In any event, I am hoping to gather some opinions on the some various basic issues about what to do next.

First, if anyone can suggest a great book (or other resource) on flash I would appreciate it.

Second, since I learn by doing I will likely purchase a unit in a week. The apparent choices are the Minolta 5600HS (assuming I can still find one), or the Metz 54MZ-4. If anyone has any advice on which unit might suit my ignorance I would also appreciate that.

Last, ignoring my ignorance, does anyone have any purchasing thoughts regarding the two. With respect to this I am wondering if the Metz might have a built in advantage due to the widespread calibration issues for the 5600 - obtaining service and or calibration might be difficult. Does this factor alone almost necessitate the choice of the Metz?