There are a number of certified mountain guides and leaders who, besides the traditional mountaineering activities, also offer trail running programs. Some of them for people who just want to have a taste or get introduced into the discipline, and some other for more experienced trail runners who want to improve their skills or get prepared for races.
The benefit of going with a guide is that they not only help you develop your potential, but they know the terrain and can take you to the best places for trail running in a safe way. It makes a huge difference to go over the different aspects you must pay attention to with a specialist: Mental preparation for long distance running, physical preparation, training, planning, race technics, race management, nutrition, safety technics and necessary gear.
And with a guide you can pay special attention and improve your technical progression. Not everything is as intuitive as it may look when running in the mountains: you must know how to run down, how to use poles while going up, and where to set the foot, in order to avoid injuries. And, most important, how to increase the distance progressively, especially when dealing with high altitude.