I have just purchased a new lawn mower and am wondering about the maintenance. I'm not very good at mechanical maintenance and without a small engine shop in my local home town I'm wondering what I can get away with. The owners manual says to change the oil after the first five hours of use, but is this really required? Will my new lawn mower stop operating of I don't do this first 5 hour oil change?
It (probably) won't suddenly stop and refuse to start again after 5 hours of use, but it's a good idea to follow the recommended cycle: the parts in new engines often haven't been milled perfectly smooth, so as your new engine turns those rough bits get knocked off or cut tracks for themselves, leaving little pieces of metal in the oil. Unless you get rid of them by changing the oil, they can cause excessive wear and tear on the engine.
Depending on your lawnmower, you'll either be able to drain oil out of the bottom, or tip the mower over and drain it out the top from the same hole you pour the fresh oil into (the worst part of this is lifting and tilting the mower over the catcher pan, but it's a lot easier if you have someone to help).
I also got a new mower recently and just changed the oil this weekend, having used it a few times since I got it (several hours at least).
The stuff that came out was truly done -- black and burned. So it certainly needed it!
Follow the manual. I'll probably change mine a few times during the season since I really hammer it with tall wet grass and weeds sometimes, causing it to stall and also get pretty hot. It's easy to do, all you need is a pan to drain it into. Make sure you don't overfill it when you add new oil in.
Make sure you use oil rated according to the manual (mine's SAE 30) since it can get pretty hot in a small engine without active cooling.