Tuner question What are Gang Stages, What is RF?

You have a lot of reading to do...gain stages don't mean much as a general term. Find manuals or reviews on older Mac, scotts, fishers, sansui and marantz tuners. Read, read, read...Check out Magnum Dynalab also.
They can all be really good or really bad

Check out http://fmtunerinfo.com/. There's a whole section on gangs and filters (see the menu on the left).

Dick