Hey Mike.
To do an oil change, empty the gas tank first. Remove the oil fill cap/dipstick and check the oil level to see if it is overfilled. Your model doesn’t have an oil drain plug, by the way. Position a catch pan on the oil cap side of the mower and tilt the mower over on it’s side (oil fill tube side) and allow the old oil to drain into the pan. Then set the mower back onto all four wheels.
If there was too much oil measured on the dipstick, earlier, remove the spark plug and pull the start cord several times to help evacuate any oil that may be in the cylinder. Clean and inspect the plug, and make sure it’s properly gapped, then reinstall the plug (or a new replacement plug) and reconnect it’s boot. Also, check the air filter and clean or replace as required, at this time.
Carefully add new engine oil in increments, taking care not to overfill, until the correct amount registers on the dipstick. Then cap the oil fill tube.
Add some fresh gas (marine gas would be a better fuel as opposed to “super unleaded”, by the way), and try to start the mower. Allow several attempts, as the fuel likely lost it’s prime during the service just performed.
If you still have a no start result after your fuel supply to the carb is re-established, the carburetor might be varnished – usually caused by leaving fuel in the system for too long. The metering needle, jets, etc., may become clogged or glazed with the old fuel, which tends to become sticky (like varnish) and sneakily alters the prescribed air:fuel mixture. Blowing things out alone won’t likely solve this problem. You’ll either need to thoroughly clean the carb using carb cleaner and fine gauge wire (s), plus compressed air, etc., or the carb may need rebuilding or replacement.
Hope this helps. Good Luck.