Prior to Moses, under Moses and after the cross, there was one gospel that brought salvation. Under both the old and new covenants there was a church that served as a means to unite believers. In both as well, God conferred responsibilities upon a priesthood of all believers.
And ye shall be unto me a kingdom of priests, and an holy nation. These are the words which thou shalt speak unto the children of Israel.
Ye also, as lively stones, are built up a spiritual house, an holy priesthood, to offer up spiritual sacrifices, acceptable to God by Jesus Christ..... But ye are a chosen generation, a royal priesthood, an holy nation, a peculiar people; that ye should show forth the praises of him who hath called you out of darkness into his marvelous light.
I Peter 2:5 & 9
Evangelicals use I Peter 2 to support their theory that a priesthood of all believers replaced the ministerial priesthoods of the Old Testament. In both the Old and New Testaments, there certainly was a universal priesthood of all believers who had sacred duties, but there is no indication in either testament that this replaced the ministerial functions in Christ's church.
If ministerial functions were replaced by a priesthood of all believers, why are offices like pastor, elder and deacon so frequently evident in evangelical churches? Why not entrust the functions previously performed by God's ministers to the laity and have them preach every Sunday? Why do evangelical churches rely so heavily upon one central personality to provide spiritual guidance and leadership?
There certainly was a priesthood of all believers in the New Testament church, and they had sacred responsibilities before God. But there is no evidence in the Bible that a priesthood of all believers usurped the authority of ministerial functions in Christ's church.