questions

i know you all probally get asked tons and tons of questions. however, just one more time please.
my sister is lds/mormon, not polgamy, just the straight lds. and her daughter is lds/mormon. and its like , some of the values and strict rules about certain things are just awesome. i am catholic and my other sister is baptist. so we seem to have a wide variety of different faiths.
question time now..
when a man takes another wife or sister wife, do they actually go down to the courthouse and make it legal? or is it done between the family?
does the prophet assign wives to men?
how many wives can one many have?
if a wife leaves, can she take her children with her. i mean like leave the compound or where ever they live.
last one.. for now that is..lol...
why is it, that the lds, the main body of the mormon faith, does not agree with polgamy? when at one time, they themselves believed and lived a polgamy lifestyle??
thank you for your time..