I would assume that the deck can easily be welded, at a minimal expense if
you find the right shop. Try to find a small machine shop or welding shop,
and take it to them for an estimate. Welds of this type don't always look
great (an obvious patch) but functionally, they are perfect. I know
because I have one done, and the old deck then outlasted the engine.
For the blade, call any mower shop and tell them your model mower, and ask
them for a new blade price and a sharpening price. The sharpening price
should be cheaper. Make sure that they balance the blade when they sharpen
it, otherwise you will get vibration.
Hope this helps.