First off the easy one... remove the lower part of the sheild (the one that gose underneath the Amiga) from the Amiga.
If you want you can then lightly grind away the rust if you want to save the metal sheild (usually not needed).
For the RF... it's soldered with 3 legs if I'm not mistaking... desolder these to remove the RF. Then remove the top cover by simply pulling it off (the lower part I'm not sure if it's lose or fixated in some other way aswell). Grind away the rust CAREFULLY as we need this sheilding again and don't want to bend it too much out of shape.
That's what I would do... if it fails I'm willing to buy that scandoubler of yours. ;-)