Hi Ricardo,
First, a few words of disclaimer. My grappling experience is in BJJ, including gi and no-gi/submission grappling, judo, and a tiny bit of shuai jiao and catch. I have never trained any of the various forms of wrestling (greco, freestyle, folk, etc) or sambo. Those arts have some significant differences in rule set, especially in regards to pinning, so some of what I say may be different there.
If you want to add neck work, you can. I personally do not, for the simple reason that, as an amateur grappler and a professional health-care practitioner that works with a lot of grapplers, I simply don't see it preventing injury. If anything, the people I work with that do a lot of neck work tend to have more screwed up necks, upper backs, etc than those who do none. Furthermore, from a performance standpoint, neck work makes no difference in resisting chokes against someone who knows what they're doing, especially not in the gi, which is more my focus.
Now, this is my personal opinion, based on my own experience. Other people will disagree, so it's ultimately up to you to decide for yourself. If you do go that route, Pavel has some excellent neck drills in several of his books, and the standard bridging exercises that you see from wrestlers and some judoka are fine as well. If you decide to do them, I would progress very cautiously; I know a lot of people who have injured themselves doing the exercises, which is obviously counterproductive. If you get hurt in competition, it happens. Getting hurt in rolling/sparring can happen, but shouldn't. Getting hurt in training is a clear sign of doing something wrong.
Also, keep track of how you feel and how you're doing, and if you're getting anything out of neck work. If not, drop it. Anything you're doing you have to recover from, and people often get caught up in adding so many little extras to their bjj training, they don't realize how much it's taking away from their actual grappling. I've definitely been guilty of this. If you have neck pain, stiffness, or other issues, consider all the possible reasons why that might be, and explore various possible fixes. Some people swear by neck training, but it's not a panacea.
For boxers, neck training serves a more direct role, imho. But that's another topic, it's been years since I did any kind of striking art, and even at my peak, I did not train with the calibre of strikers equivalent to the calibre of grapplers I train with now.
