Repair or replace?
That depends on the roof's age, how it's failing, how many layers are already on the deck, and whether a durable repair can actually tie into the existing system.
What causes ice dams?
Heat escaping the living space melts snow that refreezes at the cold eaves — the fix usually involves attic insulation and airflow, not just an eave membrane.
Should flashing be reused?
Only if its condition, material, and geometry allow it to be integrated correctly — reusing it to save a step isn't a good enough reason on its own.
Can I inspect the roof myself?
Not if it's steep, wet, icy, hot, or already damaged. Observe from the ground or an interior vantage point and leave the roof itself to a professional.