Thanks for your feedback guys.
Deejay, your plan of attack sounds like the way to go.
This morning I decided to drop the mower off at a reputable service centre near me. They will be the ones doing the sharpening when I get to that point. I have asked them to have a look at the mower and give me a list of everything that needs repairing/replacing. They are going to do this for me for $30, I think that is money well spent. When I get it back I will post the list of repair items and get further advice about which things I can tackle myself. (Hopefully everything except the welding).
I asked them about the broken chassis rail and how they would fix that. Their response whas that they usually reweld where it is broken and then weld a strengthening bar inside the C channel. Does this sound like an acceptable way to repair this problem or would you only recommend removal and replacement of the broken rail?
Steve