Film is, in many ways, not that different than digital photography. The film (sensor) is still exposed to light for a fraction of a second, creating an image. The major difference is that the image is not immediately useable.
You don't say what kind of digital camera you are used to using. If you have only used a digital point & shoot, automatic-everything, camera, then the Spotmatic will seem like an entirely different world.
First of all, it is strictly manual focus. The good news is that the faster lenses that were common back then and the larger viewfinder with a split-image rangefinder focusing screen, make this less intimidating than it might seem.
Secondly, the exposure meter on the Spotmatic does not control the exposure. It merely informs you when it thinks you have chosen the "correct" exposure.
Thirdly, in the case of the Spotmatic, you must use a technique called "stop-down" metering, since the camera lacks the communications with the lens to inform the meter of the selected aperture. This means that you must first focus the camera. Then, push the little black switch on the side of the lens mount up. This turns the meter on and stops the lens down to the aperture selected on the lens. By rotating the aperture ring and the shutter speed dial, you center the meter needle in the viewfinder.
At this point, the meter thinks your chosen exposure is correct, but you are free to override it. For example, if you see that the image has both brightly lit and shadow areas, you can either stop down a little more to protect the highlights from being blown out, or you can open up a little to bring out the shadow detail. With experience, this will become second nature.
I suggest you get two publications: the Spotmatic II operator manual, which can be downloaded for free from
http://www.pentaximaging.com; and "Understanding Exposure" by Bryan Peterson. The former will explain all the arcane workings of your camera and the latter will explain in great detail and clarity, how "proper" exposure is achieved.
Peterson's book is also useful when using a digital camera, since the the three elements of exposure (aperture, shutter speed and film/sensor sensitivity) have the same relationship in both media.
The Spotmatic family is/was a great camera line. When new, it was one of the best selling SLR cameras in the world. It can still make amazing images. The Pentax lenses of the day are ranked with the best. Plus, there are literally millions of lenses, both from Pentax and others, that will fit your camera.
I've never used the Ilford film, but Kodak also makes a "chromogenic" B & W film that can be processed in standard C-41 color processors. You may find it a little easier to find.
If you really get hooked on B & W, you may want to consider using "true" B & W film, such as Kodak's Tri-X, and develop it yourself. It really isn't hard and requires only a little, relatively inexpensive, equipment. Its also a lot of fun.