I agree with Kfamr. Don't tell your parents you are going to start being more responsible just do it. Then when you bring the subject up you can ask if they've noticed how you've been feeeding/walking/cleaning up after Katie without being asked, or how you've been taking out the garbage/cleaning your room/doing the dishes etc without being asked.
As for deaf dogs they can be quite a challenge, especially if you don't have a lot of training experience. That doesn't mean it can't be done though. Your whole family has to realize what a challenge it will be, albeit a rewarding challenge. You may end up with a dog that can never go off leash, although some can be trained to respond to a vibrating collar

I know a lady from another board that does deaf dog rescue. I asked her for some links, and while she hasn't gotten back to me yet, another person on those boards who's adopted a deaf dog from her gave me these:
http://www.deafdogs.org/

http://www.deafdogsatlas.com/

And finally a deaf dog message board that I believe is run by the rescuer I mentioned above:
http://www.voy.com/140866/

Anyways, good luck with your plan, I hope it all works out.