I would replace the needle and seat kit, the seals on the emulsion tube, fuel line, float and if the bowl is corroded on the edge- replace that as well. Yes on replacing the breather hose, plug and air filter too. It will not directly cause the runabilty condition- but will shorten the life of the engine further. That is if the screws that retain the filter base are there as they need to be installed to prime and run up well.

After you hae spun the engine several times with the plug out, replace the plug and leave air filter off for the moment. Engine should now crank and run, but plug may foul, meaning you have to clean oil off plug, reinstall and crank again. Once the engine starts, it will smoke like crazy, then clear up, and then begin to smoke again. This is normal. First smoke is oil in the combustion chamber, intake manifold, etc. When it starts smoking a second time, this is oil in the muffler, now hot enough to burn off. May take as much as 15 minutes or more to burn off completely. You make need to use a squirt of gasoline or starting fluid to get engine to light off initially. Use sparingly. Finally, don't forget to replace air filter.

Per your email "From another site I saw this... please? do not tip the mower with the air filter facing up, this allows the oil to seep out through the valves and on to your driveway, also when you go to start it up, chances are you will be out of pocket the money plus some more that you will have to pay in order to have someone that knows something about small engine maintenance to repair the damage that was done by doing this stupid move. Comments please." In the perfect world, a four cycle engine would remain in the orientation to which it was mounted. The very next best position is with the spark plug pointed into the sky. The problem with that is a typical walk behind that is tilted back on the handle doesn't give you much room to see where to scrape. The key to cleaning a mower is to get the job done quickly. Once again, the key to cleaning a mower is to get the job done quickly. If I have a mower on it's side for 15 minutes, a small amount of oil can seep up the valve stem and some residual oil finds it's way into the muffler. It is even possible to hydraulically lock an engine when too much oil seeps into the cylinder. It becomes an inconvenience, not a part changing costly repair. Variables in engine design, wear, valve orientation when shut off can come into play, but only when the unit is tipped for a longer period of time. The only damage that could be done would be to damage the paper media of the filter. Tipping with the filter up protects the filter media from damage. Best of luck on whatever you decide to do. You may help others by keeping the conversation on the board for all to see.

Call the manufacturer of the boiler for local parts sourcing. Most every boiler using a combustion chamber has replacement kits. I've had mine replaced once. Not a big deal. Got the replacement through a local hardware store that dealt with the boiler company's parts. Search combustion chamber+"your brand" using search engine. I see Weil McClain kits going for &$50-70 bucks. These get cracks in them from age, but more so from rookie technicians that hit the pot with their flush brushes during cleaning.