Hi, my wife an I have had this ongoing question since we converted. We married 10 years ago in valid, natural marriage. We were very secular and had a female justice of the peace marry us . Anyway 8 years later by the grace of God we found the Faith and converted. Since we were both unsure of the validity of our (protestant) baptisms we were conditionally baptized. During our catechesis our SSPX priest said something along the lines that our marriage would be elevated to the status of a sacrament once we converted. I am not sure how accurate this is, and during our current priests homily yesterday made us think while our marriage is certainly valid, it may not be a sacrament. Which is correct? and what can/should be done about it? We attend a SSPX mission chapel.

I would agree with the first SSPX priest here, but don't have any evidence to back it up.  What did the second SSPX priest say that made you doubt it?  In any case, I think it probably wouldn't do any harm to repeat your vows in front of a priest now that you're Catholic and validly baptized ... to remove all doubt.

He said if two unbaptized Catholics get married it is a natural marriage but not a sacrament. 

I'm not sure what "unbaptized Catholic" means; there's no such thing.  What I'm guessing you mean is two people who are not baptized Catholics.

That is true, but the other priest was saying that once you become Catholic, the marriage would be elevated to the state of a Sacrament.

I'm sorry I typed that wrong. I meant two unbaptized people. 

Something about the automatic changeover from civil to Sacrament sounds wrong to me.  Where does the requirement for proper form, matter and intention fit in?  Is the form the same in a civil marriage? Is the Catholic intention?

So, marriage is a bit different from the other Sacraments, but the validity depends upon expression of the contract for an indissoluble bond, and thus is the same for the natural equivalent and the Sacrament.  But only Catholics can have the Sacraments, and so when contracted among non-Catholics it's not a Sacrament, but contracted among Catholics a Sacrament.  But the essence (matter/form) is basically the same in both cases.  From another perspective, Sacraments confer sanctifying grace, and non-Catholics cannot receive sanctifying grace.

Perhaps one analogy would be with the Sacrament of Baptism, though it's not perfect, where if you were to baptize someone who lacked the proper dispositions (let's say he doesn't really believe and isn't contrite, but just going through the motions for social reasons), the matter/form would be validly conferred, but no sanctifying grace would be transmitted.  But if later the individual came to believe, had contrition for his sins, and went to Confession, the Sacrament would have its intended effects, putting the soul into a state of sanctifying grace ... and the matter/form would not be (and cannot be) repeated.