Do I need fasteners to install this, or does it come with hardware?

Handle assembly ships without fasteners. You'll need the original mounting bolts from your old handle or source M-series hardware from your local supplier.

Will this fit all four doors, or just the rear left?

This is rear left only. You'll need separate handles for the rear right, front left, and front right positions.

Can I install this myself with basic hand tools?

Yes. Remove the door panel, unbolt the old handle from inside, bolt the new one in place using the same mounting points. No specialized tools needed.