Thrawn Janet-I need help with the dialect

There was nae doubt, onyway, but that Mr. Soulis had been ower-lang at the college. He was careful and troubled for mony things besides the ae thing needful. He had a feck o' books wi' him--mair than had ever been seen before in a' that presbytery; and a sair wark the carrier had wi' them, for they were a' like to have smoored in the Deil's Hag between this and Kilmackerlie. They were books o' divinity, to be sure, or so they ca'd them; but the serious were o' opinion there was little service for sae mony, when the hail o' God's Word would gang in the neuk of a plaid. Then he wad sit half the day and half the nicht forby, which was scant decent--writin', nae less; and first they were feard he wad read his sermons; and syne it proved he was writin' a book himsel', which was surely no fittin' for ane of his years an' sma' experience.__

What is the meaning of "sair wark the carrier had wi' them, for they were a' like to have smoored in the Deil's Hag between this and Kilmackerlie."?
Does it mean "he was too busy with his books"?

What is the meaning of "but the serious were o' opinion there was little service for sae mony, when the hail o' God's Word would gang in the neuk of a plaid."?

The first sentence is about the poor carrier who brought all the books from Kilmackerlie.

hard(or difficult) work the Carrier had with them for they were - like to get- (nearly got) bogged down in the devil's bog between here and Kilmackerlie.

serious folk were of the opinion that there was no need for so many (books) when the whole of God's word would go in a small folded pocket. (probably a reference to a pocket bible)

Many Thanks.