[NoMoSno]

If the drip edge is in good shape, I wouldn't bother with the added expense of removing the gutter, then replacing.
It's pretty hard to re-roof and save the ridge venting. Ridge venting is not expensive, material wise.
I was given a choice, if I wanted aluminum or shingle over (with added cost)
They still sell shingle over ridge venting. My opinion it would look better on a hip roof.
Might want to get a #3 roofer bid.