Connect my PC VGA to my (really old TV) input.

You will probably need a VGA-to-NTSC converter.  The data and scan rates of the two devices do not match.  This search will bring up a bunch of them: https://www.google.com/search?q=VGA-to-NTSC+converter

However, you will spend about as much for a VGA-to-NTSC converter as you would for a small flat screen TV with a VGA input.

Actually, VGA is already an analog signal, so it's relatively easy to provide a composite output signal from a VGA output ==> this will do it for less than $10:
http://www.amazon.com/Converter-Composite-S-Video-Supports-Resolution/dp/B007DNB6D2/ref=sr_1_fed1_4?s=electronics&ie=UTF8&qid=1356174783&sr=1-4&keywords=vga+to+ntsc+converter

Assuming your "... plug-in type input receptacles ..." are a composite video input and audio input; this box is all you need.    Your PC's audio output can be directly plugged in to the TV's audio input with a simple cable that has the appropriate ends.    [Most likely something like this:    http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10218&cs_id=1021804&p_id=665&seq=1&format=2

First check whether your PC's graphical card includes an "s-video" or TV Output. Many video cards include that. If not, I suggest replacing the video card of your PC with one that includes such an output. Then all you have to do is connect the TV to that output and select something like AV-in or similar on the TV, and on the PC change the display properties to use that output along with the standard VGA output. That way you can display things on your standard monitor as well as on the TV. The output looks similar to PS2-keyboard or mouse output's, but those won't fit in.

You'll have to be aware that old TV's have a terribly low resolution, lower than standard VGA (640x480), whereas the resolution of PAL is a little better than NTSC. So chances are that you won't really be happy with the output. You'll only be likely to get better resolutions with newer flat panel TV's, and those usually also include VGA, DVI, or HDMI inputs so you can connect a PC using it's standard output easily.

I need to have a look behind my PC and my TV-connected equipment.

Will get back to you.