Lots of parishes encourage 'registration' as a way to keep track of who is and is not in the parish. It comes in useful for things like the diocesan census that gets taken every couple of years. I wouldn't worry that you are signing up to something too major; in most parishes it is very common (in fact a few churches I know of have registration forms in the church porch for people new to the area).
With regards to reading at mass it is a very special thing to do; you may be nervous when you start, but stick with it and it can be very rewarding for your own spirituality, as well as in the context of serving the community.
Someone mentioned that a Deacon should do the reading if he is there. I don't think that is true - a Deacon should always proclaim the gospel is present, but the first and second (if applicable)readings should be performed by a suitable instituted lector (i.e. not an ordained minister). Someone more learned than me regarding the GIRM might be able to clarify this.
I'd also echo what was said about cantors (and whole choirs) - music is and has always been central to the mass, and a cantor is as important as a lector or acolyte (read: altar server); just because we can get away without cantors at some masses doesn't mean they shouldn't be there, any more than we should just shrug our shoulders if there isn't any altar servers today.
All the best