There are no "Dumb" questions here.
Yes, the stocks from a Topper Deluxe Classic will fit on a Buffalo Classic. That's a good choice, IMO. Those walunt stocks are real nice.
I can't answer the question about the conversions, but I am sure someone will chime in with answers to that for ya.
As for being kept up at night...Do you think you are alone? There is no cure. We "Handiholics" just have to deal with that. LOL
I don't know if the TDC stocks are available, yet, from the factory. They are still trying to get out the TDC 20ga models and may not be shipping any for accessory orders. You can find the email address and phone numbers for the factory in the Sticky at the beginng of the forum pages. Give'em a call or send an email and they can answer that for you.
Good Luck with your BC. Post a pic when you get it all together.