Combines bigger tires do I need longer feederIJ

No you don't need a longer feeder. You just need adjust the front of the feeder. There's two pages in the Operator's Manual that will show you how to change it. If you don't have a book I might be able scan the pages for you. Might be a day or two thou.

The ladder and cat-walk can be extended by adding bolt on sections. You might check salvage yards.