Regarding the bridge:
1. go buy an electronic tuner
2. Measure the distance from the nut (the piece of white plastic/bone material just above the first fretwire) to the 12th fret.
3. Measure from the 12th fret to the top of the mandolin and position the bridge perpendicular to the strings at that point (it is usually about the mid-point of the f-holes).
4. Bring a few of the strings up to pitch (or close) and then see if the note at the 12th fret is the same note as the open string (it will be one octave higher, but the same note).
5. If it's flat on the 12th fret then you have to move the bridge toward the nut if it's sharp then move the bridge away from the nut.
When you get the bridge positioned at the right place, bring all the strings up to tension and voilla - your done!
¡papá gordo ain’t no madre flaca!
'20 A3, '84 1N, '84 A5-1, 2012 Cohen A5, 2012 Muth A5