For a developing bowler, a wrist guard is not a bad idea...
Depends a bit upon your style - are you a stroker, cranker or tweener?
Crankers can't use wrist-guards effectively by virtue of the fact that often their revs are produced by breaking their wrists deliberately.
BUT - wristguards definately increase consitency, and help you develop strength and muscle memory while you use them. I used one for about two years before I developed a game without it. I still carry three different ones in my bag for practice occassionally or correcting faults if I feel them developing (actually I lie, I only carry 2 now, I gave one away)....
If you are a developing bowler it is certainly worth considering (which you obviously are), but I would seek the advice of a coach before buying one. Get yourself a couple of coaching lessons and see what the coach says...
Some wrist guards cost over $110, so spending $40 - $50 in a couple of coaching sessions would be well worth while (and half the cost of a wrist guard). It may turn out that you need one, but at least you will know for sure and the coach will explain to you why and how best to use it (as well as the best one to get for your situation).
Whatever you decide, good luck with it!!!
PB