Since I plan to do a piece or two on Textual Criticism, I thought I'd say just a few words about what that term means ... because, in my bitter experience, even very well-informed people often misunderstand it. You can even find the term misunderstood in otherwise respectable books.
Textual Criticism does not mean commenting on a text; going deeply into its meaning; explaining to people who don't understand it what the author was getting at; still less, criticising it in the sense of explaining why it's wrong! NO! It means this: -
Pre-modern and early modern texts rarely give us that text as it sprang like Athene straight from the head of its author. Almost invariably, a text has been transmitted by scribal copying, during which changes will have been made. Sometimes these changes are mistakes (like leaving out a line in error); sometimes they are intentional (I can improve that; or He can't really have meant that; or I think I'll bring this verse of S Mark into line with the parallel passage in S Matthew; or This is in rather awful Greek ... I'd better correct it ...etc. ad infinitum). So you will find that no two manuscripts are entirely the same.
Textual Criticism means using very many different skills to try to get back, from the available copies, to what the author actually did write. Although ... many of us now doubt whether the 'original text' really is always ascertainable, because in the Ancient World at least some sorts of texts existed fluidly rather than statically ... a bit like your favourite Cookery Book in your kitchen, where you have entered in some of your own discoveries ... changed the quantities here ... extended the times because of the idiosyncrasies of your own oven ... written in a new recipe there ... Shakespearian scholars among you will know that, even after the invention of printing, Textual Criticism still cannot be avoided, because the questions of 'Actors' copies', modified within the actual process of dramatic production, and of 'pirated' editions, published from a shorthand copy, crop up. And have you ever looked at the Oxford Edition of Wordsworth? Phew!
The Magisterium of the Catholic Church has employed Textual Criticism; perhaps most notably when S Jerome and, later, Roman Pontiffs were working on the Vulgates and when S Pius V had the Missale Romanum revised; so don't be afraid of it!