From what little I know, Stealth for a char. is how silently they can move, i guess, so if Minsc was invisible by a spell, he would depend on his stealth to keep himself from being heard walikg, because surely an invisible man can be heard, if not seen. So stealth plays a role in that.
For the second question, you're right, you make an attack out of hide in shadows, and the guy did not know you were there. But you have to make a sucessful role to hit, and also I think against his seeing you coming or something. The higher your level and such, the better the chance, but also how good is the opponent's level?
Does that rambling make any sense?????
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Larry, Sell-Sword to the OHF