Microscope lens and DSLR connection info

I have just started macro photography and I use a Canon DSLR and a 100mm Macro lens at f/2.8. I have my DSLR attached to the Stackshot rail for stability. I have the Raynox 250 on order.

I have seen great photos using microscope lenses attached to the DSLR but cant find info on how to connect them and what parts to use. I did a search on google and was overloaded with choices, some being exotic and over my head in complexity and cost. I am looking for a simple way of setting this up.

I need info on:

1. What are the common Microscope lenses used and can they be bought on Ebay?

2. What interface is used to connect the Microscope lens to the DSLR lens?

3. What is the best DSLR lens to use in this process?

4. What can bellows be used for?

5. What to avoid and not waste time and money on.

Thanks for your input.

Dwight