First, I'd have to say that GTD is harder than you think it will be. Its alot to manage and if you are comfortable with the system you have now you may be better off keeping it.
Second, there seems to be an all or nothing mentality about GTD sometimes. I have found that just implementing a facet or two can really help. You might want to consider a partial implementation. In fact, thats all I've been able to manage up to now.
Mark in Texas