No problem, Tom. Oil gets dirty rather quickly on side-valve Briggs engines like yours, but in this case we have no way of knowing just how long it has been in there, or how foul it is, so it will have to be changed. You get the best results changing oil if the engine is run for 5 minutes or so to warm it up before it is drained, for two reasons. First, when the oil is warm it runs out easily, so more of the old oil can be removed when you drain it. Second, when it runs it stirs up the dirt that is laying in the bottom of the engine, so if you drain the oil immediately after running it, quite a lot of the dirt runs out with the oil. I suggest you get everything set up for the oil change, including something to drain the oil into, and a stable stand to put the engine on while it drains. Find the right size and kind of spanner (it will have to be an open-end spanner: you can't use a ring or socket on a square drain plug) and put it near the stand. Then put the engine on a flat, strong surface so you can start it. Before you start it, practice stopping it. Your engine is stopped by flipping the vertical metal piece beside the spark plug, sideways so it rests against the top of the plug. Flip it back and forth a few times to get the feel of it. Then figure out how you are going to operate the choke, and the speed control. The choke is a simple pull-device on the carburetor, right under the air cleaner. The speed control is normally operated by a lever on the handlebar, but you have disconnected that to take the engine off the mower. Take a look at these parts and tell me how you are going to operate them, before you start the engine. Please post pictures, so we are all talking about the same things.
To post pictures, just use the icon that is fifth from the left in the row of icons at the top of the posting box. Then press "browse" and find your pictures on your hard drive. Click on the first picture, and then on "add picture from my PC". After it finishes loading, browse to the next one, and so forth. When you have loaded them all, click on "all done".
