Yes! Yin can be very beneficial for you if you are a runner. First let's talk about the benefits, and then talk about when is best to do it.
From a physiological point of view, running places a lot of stress on the knees, hips and lower back. While the muscles that move these joints do get stronger the more we run, they can also get tighter. Many professional athletes require tight muscles to give them a springing effect (think of pro basketball players: they do have quite tight hamstrings, and that is what helps launch them up to the basket...the tight hamstrings act like springs.) However, us "normal" people who are more concerned with running for health reasons rather than performance reasons, do want to have a reasonable degree of flexibility and range of motion.
Chronically engaged muscles tend to shorten, which creates tightness and reduces our range of motion. The reduction in the range of motions comes both from the muscles shortening but also from the joints tightening. Yin Yoga will help open the joints back to their normal range of motion (which everyone, including pro athletes need) and will help to stretch out the fascial bags that encase the muscles. In short, Yin Yoga will help regain the natural range of motion for all areas of the body tightened by running: the knees, the hips and the lower back.
From a mental point of view: we all know that running can be a meditation. Sometimes however, our minds are just freely floating while we run. It is not a meditation at all; it is an escape. In our Yin Yoga practice we can train the mind to focus, concentrate and enjoy the present moment. With this training we may find that we are more present while we are running, allowing us to enjoy the scenery or appreciate our body while we move.
Finally: when best to do Yin Yoga? If the intention is to work the physical body and open the deeper connective tissues, this is best done before a vigorous workout. We would like the muscles to be cool so that the stress of the yoga practice goes deeper into the connective tissues. (See this post on when it is best to do Yin Yoga:
http://www.yinyoga.com/forums/viewtopic.php?t=398 Or this one:
http://www.yinyoga.com/forums/viewtopic.php?t=352)
Hope this helps you enjoy the yin-side of running. You also asked about yang yoga: yes - this too will help you with your running. There are many web sites that can guide you, for example:
http://www.yogaforrunners.ca/resources.html)
Cheers
Bernie