My tablet's pen is one that I have instructions how to take apart if it's so needed. Would yours so happen to be like that? I don't remember how the Wacom's are anymore. (Unless you could get in touch with someone from the Wacom site? Took a look there and found this: [link] )
Did your tablet come with a nib tool? It's made for grabbing short nibs and pulling them out. (it's basically a small ring of sheet metal with a hole in the from on it so you can grab the nib) If you don't have one, a pair of needle nose pliers (or something similar) could work.