2. Logic cannot open VST Plugs, only AU plugs which should be located in the directory: (whatever your hd is named)/Library/Audio/Plug-Ins/Components
Then, to open plugins click an hold on the instrument name in the channel strip and scroll down to AU Instruments then your plugs are organized via developer, select the instrument and your good to go.
Don't mean to sound like I'm patronizing you, question 2 just lacked some clarity. Although, I haven't tried it you CAN use VSTs in Logic if you first download a VST wrapper and I think that it has to be a Mac Intel ready VST. I think that FXpansion has a wrapper but I'm not positive.