Bicycle Mechanics - Headset issue

I've just noticed that my headset appears to be loose..I can hold the handlebars and move the frame ever so slightly up and down. Problem is, I don't know whether my headset is a threaded or non-threaded headset. Can it be adjusted, or is it time to replace parts?

I've read some instructions online on how to identify my headset type, but the lingo just doesn't jive with me.

Below is a picture of a similar bike, but the part that attaches the handlebars (the gooseneck?) looks exactly the same, as well as the headset setup below the handlebars.

http://img.photobucket.com/albums/v488/joshy380/bicycle-757253.jpg

http://www.parktool.com/repair/readhowto.asp?id=127

http://www.parktool.com/repair/readhowto.asp?id=127

Very helpful, thank you. Now I know that it's a threaded headset.

Now then...it would appear the upper cup has a slight gap between it and the head tube. Is it possible to use a mallet to close that gap, or is it absolutely necessary to buy the specialized tools? Or am I just better off taking to my LBS and letting them fix it? If so, what do you think they might charge?

It is VERY helpful to have previous experience or expert assistance on hand for proper adjustment of a headset. However, the only "specialized tools" needed should be headset wrenches, unless something major is wrong with the headset or its installation. I'd seriously consider having a LBS take a look at it at least to see if your observed gap is normal or abnormal.

That said, I have used a mallet to seat the headset cups those last few mm. Just don't hit very hard and lay a board across the top so that you know the force will be evenly distributed.

....it would appear the upper cup has a slight gap between it and the head tube. Usually the head tube is cut flat, while the upper cup may well be a tad conical on its underside. What looks like a crack may not be functionally important.

....Is it possible to use a mallet to close that gap, or is it absolutely necessary to buy the specialized tools?
Simply banging on it is unlikely to be successful. If you want to continue the DIY-approach it's better to find some threaded rod, 10-12 mm dia, and some BIG washers. Thread rod through head tube, put washers against each cup, get some nuts on and torque away.

A gap might indicate that it needs a spacer. I reiterate Mondoman: It takes experience. Do take it to a shop. Ask to watch so you can learn. And read up on the subject in your spare time. You don't want to "experiment" with your steering-mechanism.