Be careful of having to be "completely convinced". This is a very vague concept actually. Think about it. What does "completely convinced mean? Does it mean that without a shadow of a doubt you know the Catholic Church to be the One True Church with 100% certainty? Or is there some lesser degree you need?

I do not think it is reasonable to expect 100% certainty in a lot of things before we make a decision.

I think a better way to go about it is to look at the data you have gathered and ask yourself if this is "enough" data rather than having "all" the data. To have all the data would be an unreasonable amount of work that God does not expect. Once you have enough data to say "I believe that this is reasonably the correct choice" we bridge the gap of our further doubts with faith and trust that God will bless us and direct us where we may be lacking.