In this quote from Shoeless Joe, how are the literary devices used? Also, how do the themes, symbolism, and diction of the passage relate to the story? Building a baseball field is more work than you might imagine. I laid out a whole field, but it was there in spirit only. It was really only left field that concerned me. Home plate was made from pieces of cracked two-by-four embedded in the earth. The pitcher’s rubber rocked like a cradle when I stood on it. The bases were stray blocks of wood, unanchored. There was no backstop or grandstand, only one shaky bleacher beyond the left-field wall. There was a left-field wall, but only about fifty feet of it, twelve feet high, stained dark green and braced from the rear. And the left-field grass. My intuition told me that it was the grass that was important. It took me three seasons to hone that grass to its proper texture, to its proper color. I made trips to Minneapolis and one or two other cities where the stadiums still have natural-grass infields and outfields. I would arrive hours before a game and watch the groundskeepers groom the field like a prize animal, then stay after the game when in the cool of the night the same groundsmen appeared with hoses, hoes, and rakes, and patched the grasses like medics attending to wounded soldiers.

First, in the passage, there are a few examples of figurative language. Ray says that the pitcher's mound "rocked like a cradle when I stood on it." This is a simile (a comparison of two unalike things where one thing is said to be like or as something else); the pitcher's mound is compared to a cradle, something that rocks. For obvious reasons, the pitcher's mound should be stable and not move around when the pitcher steps atop it. He employs two more similes when he says that he would "watch the groundskeepers groom the field like a prize animal" before the game and patch "the grasses like medics attending to wounded soldiers" afterward. He compares the perfectly-kept field to a prize animal who is neatly and carefully groomed, and then he compares the groundskeepers who work on the played-on, banged-up field to war medics.
I think you could, perhaps, read the work the narrator puts into preparing the field itself as symbolic of the work one needs to put into any dream. Dreams certainly become possible when one puts such honest and good work into making them come true: this is also a theme of the work. Just as Ray must tend the grass so carefully in this passage, he must also tend to himself: he has to listen to his own inner voice and trust it, as we all must.
The diction used in this passage is quite conversational. Ray uses only a little bit of baseball jargon (left field, home plate, pitcher's rubber, cases, grandstand, and so forth), but nothing so extreme that the average reader cannot understand the gist of the passage. This seems pretty consistent and expected given the subject of the entire text.