looking to wire up a subpanel in my detached garage. Here are the specs and my thoughts---

main service panel is 200amp
distance from panel to garage ~ 100'
garage will be used for mainly automotive --- lights, receptacles, shop tools, air compressor, and the big current draw = stick welder (50a)


couple questions--

1) do you think a 100a subpanel is overkill? Obviously would rather not be kicking myself down the road for having an undersized subpanel

2) if going with 100a ---- would I need to do 1/0 aluminum in pvc conduit 18" down -- fed from a 100a breaker in the main, another 100a at the sub, separate ground/neutral, add a new ground rod..

thoughts appreciated!