Residing a quonset

[DOUBLEG]

I need to do something with my quonset. The plywood ends are in bad shape, past painting. I want to put on metal siding but I don't want to redo the shingles on the roof.

What flashing do I us on the top of the siding so rain doesn't get in behind it or under the shingles?

Any ideas on how to do hang the sliding doors so they clear the siding>

Thanks.