re-painting garage siding

I have a 22' X 22' garage that needs repainting. The paint is peeling in many places, as the garage hasn't been painted in at least 10 years (maybe as long as 20 years, I don't know). The siding is the older clap-board style that is a fibre-type composition. I have a couple of questions:
1. How do I prep the job? Pressure-washer? angle grinder and wire brush? belt sander? What is the best? What is the easiest?
2. The corners are joined by sheet metal pieces. There are numerous corner pieces that need replacing, where do I get replacements? Any ideas?
Any other comments / suggestions / tips / ideas would be appreciated!
Howie Regina, Saskatchewan, Canada
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