Welcome aboard!
ISMACS has a chart for Singer serial numbers. According to ISMACS your machine is a 66 that was allocated to be built on July 6, 1953
Here's the link:
http://www.ismacs.net/singer_sewing_...-database.html
99s and 66s are almost the same. The 99 is basically a 3/4 sized 66. The tension knob is on the front (side facing you) of both machines. The 99 Has a flat faceplate, the 66 doesn't. Newer 99s and 66s have a forward and reverse lever on their stitch length , older ones have a knob you turn and no reverse. Your manual should work even if you have a 66.
Don't be afraid to clean and oil your machine yourself. There are some excellent tutorials here that will walk you thru it and IIRC your owner's manual will also tell you how. Doing your own maintenance will make you more familiar with how your machine operates and will save you some money too.
Rodney