Hi,Samovar,
For 20dn, you have a one-letter abbreviation for “priest” followed by a word meaning account books, “undertakers” in the sense of people who make a promise. The grid entry changes the first letter.
For 39ac, you have already corrected “prank” to “plank”. A “stengah” is a whiskey and soda, and you need a seven-letter word that’s an alternative spelling, into which you insert R for “recipe”. For the grid entry, change the fourth letter.