Problem with voltage regulator

Hi,

what is the voltage regulator for?
What does it do?

Some smoke came out of my voltage regulator, during the engine was running.
I turned the engine off, removed the connector, and started the engine again.
But, I think the battery is not charged anymore. Is this right? Can I drive without an voltage regulator.

How can I find out, whether it is out of order or not?

When I want to buy a new one, what is important?

At rockauto I found those: (for a Chevy Impala 350 cui 1970)

http://www.rockauto.com/catalog/x,carcode,1048845,parttype,4884

What do they mean with 37, 42, 61 Ampere?

At harmons I found this:

http://www.harmons.com/SearchResults.aspx?s1=&model=7&year=1970&s2=voltage &s3=0

Here they write something about the ampere of the alternator?

What do I need? Is it specific for the alternator? If yes, how can I find out the ampere of my alternator?

Thanks.