I just noticed that Monergism.com has posted some helpful sermons by a faithful preacher on the issue of the ministry. Here is their description and the links–
Dr. Sinclair Ferguson (born 1948) is a Scottish theologian known in Reformed Christian circles for his teaching, writing, and editorial work. He received his Ph.D. from the University of Aberdeen and has been an minister in the Church of Scotland since 1971. He has served as an editor with the Banner of Truth Trust and worked as a minister at St George’s-Tron Church, Glasgow.
Ferguson is currently Senior Minister of the First Presbyterian Church in Columbia, South Carolina. He has previously held the Charles Krahe Chair for Systematic Theology at Westminster Philadelphia. He has also taught at other reformed protestant seminaries, including Reformed Theological Seminary.
Called to the ministry (MP3)
Preaching the Word (MP3)
The minister’s prayer (MP3)