So the first question is: do you need to be registered in Poland (or any other country) in order to start getting any of the documents that are needed?
You are going to need to demonstrate that you are legally in Poland, which means you will need to show a maldunek, so you will need to registered.
And do they all need to be translated?
Yes, all of them, by a sworn tranlator, no more than three months (possibly six months, but three would be more sure) before the big day.
- a certificate of no impediment
You need to get that from the British consulate in Warsaw: they will rip you off, to the order of about £120, for putting up a notice and writing a letter. It takes a total of slightly under two weeks and you need to go there. The CNI has a 'use by date'; I think it's 90 days after issuing.
- a baptism certificate
- a certificate of confirmation
Whether you need those will depend to a certain extent to the priest (and quite possibly how generous your donation to the 'church roof repair fund' is).
Also, I have not been confirmed yet (only baptised/first communion). I have read that this might not matter, as some priests will still allow you to get married. Is that true, and would it still be a "concordat wedding" (if the priest allowed us to get married).
Again, that is going to require finding the right priest; it can certainly be done (may require a generous donation to the 'church roof repair fund').
Is there anything else needed?
You will need your original birth certificate. They will keep it.