In the Church as Jesus founded it, were the leaders called priests, and were they either required or forbidden to marry?
The leaders appointed by Jesus were called apostles. Their successors in the fullness of the ministry were called episcopoi (bishops). The Apostles themselves would establish the offices of presbuteroi (from which the English term "priest" is derived) and deaconoi (deacons) who would share in only part of the apostolic authority. As for celibacy, this is only a church discipline neither required nor forbidden in Scripture.
The first question is clearly no. Go search “hiereus” or “archiereus” and see if it is ever used for NT pastors, or if they engage in a uniquely sacerdotal function in changing bread. It's not there, only Catholic extrapolation and argumentation. See one response here .
and were they either required or forbidden to marry?
Of course, not, as instead, being married was the norm, (1Tim. 3:1-7) with celibacy having its commendation but as being gift. (1Cor. 7:7) Even all the apostles were married but two traveling missionaries.
To require clerical celibacy of almost all (and if the wife of converted clergy dies they cannot marry again) presumes almost all have that gift, which is contrary to Scripture and is asking for trouble.
But Scripture is not the supreme authority for Rome, not matter how much RCs attempt to wrest support from it for her traditions of men, nor is the weight of its warrant the basis for the veracity of her teachings, but which rest upon the presumed veracity of Rome.