Hi,
I am trying to figure out how I can reduce my 200 amp service down to 100 amps for my workshop. The panel in the workshop is rated at 100 amps and the only place that I can tie in is a 200 amp ON/OFF main shutoff just underneath the meter can on my service pole. BTW, I still have to carry the full 200 amps down the pole to my house.

You'll need to replace the disconnect at the pole with a 200A feed-through panel.
This will let you carry the full 200A to the house and also install a 100A (or less) feeder breaker to feed the shop.

Thank you sooo much for your help. I just don't understand why they couldn't tell me that at Lowe's. They kept wanting me to buy a box for this, a subpanel for that... spend, spend, spend!
Again, thank you!!

Just an afterthought... Does Lowe's or somewhere like that sell a 100 amp feeder breaker with lugs large enough to handle the 3 ga wire I have run to the pole, or will this have to be gotten from an electrical supply house?

Most 100A breakers will handle at least #2, so you are fine with #3.

Folks need to be cautious regarding advice from home centers. If home centers actually employeed plumbers and electricans it might be safe to accept their advice but they don't. It is safer to see what several experts here, and on other sites, have to say.