#1
Well i have to play Buddy Hollys Oh Boy though the song is in A our singer can't go that low so we need to play it in C and i have no idea how to transpose it and i'm at a loss..
a little help please.

Thanks.
Don't Be Afraid and just look across Blue Fields.
You'll eventually see the Fisherman's Horizon.
#3
A to C is a distance of a minor third, or three half-steps. To transpose from A to C, move every chord up by that distance. I don't know the changes for that particular song, but for example, every A would now be a C, every D would now be an F, every E would now be a G, etc.
#5
Quote by captain_jack
A to C is a distance of a minor third, or three half-steps. To transpose from A to C, move every chord up by that distance. I don't know the changes for that particular song, but for example, every A would now be a C, every D would now be an F, every E would now be a G, etc.

This is basically correct. Remember that single notes, like solos or riffs etc., need to be moved up as a minor third (3 semitones) as well.
It may help to make a chart like A - C, B - D etc.
Another way to think about it is "A is the I of the A major scale. C is the I of the C major scale, so I play C"