I been going to church about 25 adult years.
about 4 years ago i madly put my name on the readers list. my first one, i wondered if my head would stay on my shoulders etc.... I gabbled through it literally ignoring all the stuff about slowing down for the sound which i do know about. The second one I did, everyone gave me praise about how I can do it! Now I can even be given a reading five minutes before the service and will do it. We changed books in the last year and not got the new books at home. also the one service there were choices and I did ask the priest which one I should read, the day before and he was quite willing to go and select it for me, but told him, it be okay to do that next day. Next day, before the service began, He was watching out for me as soon as I was heading toward the readers stand, he came over and selected the readings. But yes, from that very first reading to now when I don't need to practice it, though obviously the sentencing does read better when I do... So yes, I can now do readings without really having seen them before the service:D
what i am meaning is it was uncomfortable at first. I still have my little anxieties before sometimes but I know I can work through them or have done so up to now. When we start something, we get cold feet at times. It is natural. It part of the process. It be worrying almost if you didn't have second thoughts. But use those second thoughts. Write them down now, in case you're asked to do some learning journal if they are still the in thing. You can capture your feelings right now and draw upon them in any assessments later.
Processsions. Most people in our church have their eye on the Priest. Yes again it nerve racking the first few times and being on the Altar is related to being on stage but you get used to it. The more you do so the easier it gets. Not everyone will see you depending where the priest suggests you sit. As an altar server I process and yes sit on the Altar. Half of the church only sees one half. Get your seat hidden by the pulpitt and even less see you. It you that feel nervous and you really do climatise. I can vouch for that. At first some will be watching you because you be new etc. But see it as encouragment and interest rather than judgemental.
And by that comment you not the best Catholic, well this sounds like you are the best Catholic to do so in that you are aware. Priests are aware of their failings and apologise as soon as they realise they've hurt someone in some way. They aren't perfect. They are human. But good ones be watching and not too big to say sorry to whomever.