Your enthusiasm is a great thing... however, get your basics down thoroughly BEFORE you go ask to shadow. You don't want to be lugging stuff around, you want to be taking pictures.
I got the chance to shadow a pro for a wedding gig once. He called me back 2 more times. Not becuase I could carry his stuff, which I did help with, but because I took some darn nice pics that both he and his clients appreciated. He asked me to shadow becuase we sat and talked for about an hour, chatted, I offered up all that I knew of a wedding gig and the related challenges. He was impressed enough to ask about my equipment, which is ok for that and then with not a lot of confidence asked me to second one gig. The pat on the back for me was when I was called back to do 2 more and the compliments from him and the B&Gs and families.
If you are a fast learner like me, you could be doing this in as soon as 5-6 months (if not, it could be a little longer, but do NOT get discouraged).
Consider taking an online course on photography.
www.proudphotography.com has an excellent internet based course for beginners for a VERY reasonable price. Buy some books on photography and psot processing of pictures, I consider these investments in myself.
A good way to know if you are ready is to go into the more advanced areas of this board here, and if you are still lost when people are discussing ISO, aperture, shutter speed and basic lighting techniques while doing a critique of someone's pictures, *and* don't know how to apply it to your camera quickly without thinking... you are not ready to go play with the "big dawgs" quite yet. If you have not gone through all of lighting 101 and 102 on the strobist board and are not comfortable with the info there... you are not ready to assist a portrait photographer. Now those are my opinions, they may not be someone else's. I think they are a fair indicator of someone that is ready to take the next step.
Take this time to learn! Practice, practice, practice and then practice some more. Make a small portfolio and then go start knocking on a few photography business doors and see if they could take in a "little to no pay" apprentice with a big desire to learn.