Just do as you would do in any other unfamiliar large gathering where attentiveness is required. If you want to kneel when others kneel, kneel. If you don't, it's fine to remain seated. It is best to stand when others stand. Remain silent unless you want to sing along with any hymns that may be sung from the hymn book provided. If you aren't comfortable with some of the words, you don't have to say them; bearing in mind that both Jews and Christians worship the same Almighty G-d, Jehovah.
The "passing of the peace" is an early part of the mass when congregants stand, move around slightly, clasp hands one at a time with several persons immediately around them and say, "Peace be with you." It's a universal gesture of goodwill to share with people if you feel comfortable; if you don't want to shake hands, just smile and nod, or remain seated if you really don't want to. Then there will be scripture readings from the Hebrew Bible and Christian gospels, some singing, usually a basket passed around for a money donation (if desired -- it is for the ongoing need of that parish, and not a gift for the person being confirmed), and possibly a short talk by the priest, as well as the confirmation ritual, at which you will be an observer in the congregation, but will not be required to do anything or repeat the creed of belief that others will say during those moments.
The last part of the mass, the communion rite (also called "eucharist"), is specifically about Jesus and is usually only for baptised Catholics; it's perfectly all right to just sit quietly or pray silently during that ritual, which is a commemoration of Jesus' last Passover meal on earth. All you would have to do is let others in your pew pass by you so they can get to and from the aisle. There are usually several other people who don't go up to the altar for communion for one reason or another, so don't feel self-conscious.
If possible, ask the person who invited you in advance to be seated with him or her, or with someone they assign to you, so someone familiar can accompany you during the mass.
Albion, I haven’t been to a RC confirmation in eons, but it HAS to be conducted by a bishop, and lasts a lot longer than regular or even holiday Masses. I’m not too sure they do collections at First Communions and Confirmations.
And non-Catholics are NEVER EVER to take Communion at a Catholic Mass. Usually at a Mass that will nave a large number of non-Catholics attending (First Communion/Confirmation/wedding) there will be an announcement with very nice, polite language telling non-Catholics that receiving the Eucharist is for Catholics in a state of grace only.
I appreciate everyone’s answer to my question. I feel lots more confident. R/Janey