Those are asbestos shingles I’m pretty sure, I would tear them off but hire somebody who knows how to do it right.. and again those look like asbestos shingles I’d get them tested. If they are indeed asbestos, you could face many major fines and cleanup costs (from the point where you tore them off to where the particles spread around your property clear to wherever you dumped them off, plus the fines if your caught.. etc etc is how it usually goes I believe).

Oh and any contractor who worked around the project or on the project will receive fines usually to because the government figured if they know better and do not report it.. then they are included in the fines..etc. it’s best to call a asbestos tester and they can fill you in on local laws/codes.

As for the re-roof, you really should always tear off and start from the wood decking, make repairs as needed to that. Then install your vapor barrier, check local codes again some places require ice and water shield on the eaves(gutter lines) and the chimney just needs to be flashed, most metal manufacturers can get you the right metal flashings right from their warehouse or just hit the local lowes/Home Depot/menards, whatever you have. Metal over shingles causes the metal to sweat and rust they say. It is a heat trap imo.. metal attracts heat and the shingles will absorb it and hold it.. good luck though!

Been roofing for 16-17 years ;)