hey White tiger,
I usually scale the object to a - depending on what axis you're using, but say you want to mirror in the x axis, then you'd want to do
scale:
x -1
y 1
z 1

Hope that helps.
As for your other question, you should really look into the vip tutorials, some really great stuff in there. Also check the tutorial forum here, there's a few links in there. I'm not sure if this one is in there, but this place has some free tuts for newbies *********************************/digital_tutors/maya/

Enjoy,
George