Do these come with fasteners and wiring connectors?

Mounting bolts and electrical connectors are included with the assemblies. Verify all fasteners are present before installation.

Can I install just one side, or do I need both?

You can install one assembly if only one window is failing. Both are included as a set, but they work independently — use what you need.

Will these work with my current door panel trim?

These mount at factory locations inside the door structure. Door panel trim removal is required for access, but no modification to panels themselves is needed.