Suddenly he heard cranes crying and gibbons wailing: the cranes' cries piercing beyond the empyrean, the gibbons' wails mournful and deeply heart-rending.

Before he sees anything he hears it, and the sound is wrong. 鶴唳 is the crane's cry (唳 lì, the particular word for it) and 猿啼 is the wailing of gibbons, which in Chinese poetry is the standard sound of grief — travellers' verses are full of it. 悲切 is mournful, 傷情 heart-rending. An inline parallel couplet, and a warning.

He opened his mouth at once and called: "Children, I have come!"

孩兒們 — "children!" He has spent twenty years as a master's junior disciple and reverts to being a father in one breath.

From below the cliff, by the stone ledges, among the flowers and grasses, in the trees, monkeys big and small alike came leaping out by the thousands upon thousands, surrounded the Handsome Monkey King, kowtowed, and cried:

Four hiding places named in a row — under the cliff, by the stone ledges, among the flowers, in the trees — and then 千千萬萬, thousands upon thousands, pouring out of all of them at once. 若大若小 is big and small alike; 坎 is kǎn, a ledge or hollow.

"Great King, how carefree you are! Why have you been away so long? You left us all stranded here, longing for you as for food and drink.

The reproach is affectionate and quite pointed. 你好寬心 — how easy in your mind you must be! 閃在這裡 takes 閃 (shǎn) in its sense of leaving somebody in the lurch. And 誠如饑渴, longing for you truly as for food and drink. (一去 is yí qù.)

Lately a demon has been oppressing us here, insisting on seizing our Water-Curtain Cave; we risked death and forgot our lives fighting him.

欺虐 (qī nüè) is to bully and oppress; 捨死忘生, giving up on death and forgetting life, is the set phrase for fighting with no thought of coming out alive. They have been holding the cave without him. (一妖魔 is yì yāo mó.)

All this while, that creature has snatched away our household goods and seized many of our children and nephews, forcing us to keep watch over the homestead day and night, sleepless.

家火 is household goods, the same word as the modern 家伙; 子侄 are the children and nephews (子 in full tone zǐ). 看守 takes 看 as kān, to watch over, not kàn, to look at. Note what has been taken: the goods, and the young.

Luckily the Great King has come — had you stayed away another year or so, even our mountain and cave would all have passed to another's hands."

年載 is a year or so (載 zǎi). Another year and the mountain itself would have changed hands. (不來 keeps bù.)

Hearing this, Wukong was filled with rage: "What demon is this, that dares be so outrageous? Tell me the whole of it in detail, and let me go and take revenge on him."

輒敢無狀 — how dare it be so outrageous (輒 zhé, to presume to). 無狀 is the very word the disciples threw at Wukong himself when he refused the four gates. And note the speed of it: he has been home about a minute.

The monkeys kowtowed: "We report to the Great King: that creature calls himself the Monstrous King of Havoc, and dwells away to the due north."

混世魔王 — the Monstrous King of Havoc. The name is built on 混世, to throw the world into confusion, and it survives in ordinary Chinese as a description of an incorrigible troublemaker. 直北下 is away to the due north.

Wukong asked: "From here to where he is, how far is the way?"

A practical question, and the first sign that he now thinks in distances he can cross.

The monkeys said: "He comes on cloud and goes on mist, now wind, now rain, now lightning, now thunder — we do not know how far the way is."

They cannot answer, and the reason is itself the answer: he comes on cloud and goes on mist, in wind, rain, lightning, thunder. That is the standing signature of a demon in this book — weather with intentions. (不知 keeps bù.)

Wukong said: "In that case, do not be afraid — just amuse yourselves, and wait while I go and seek him out."

休怕, don't be afraid (休 xiū, "do not"), and 且自頑耍, just go and play. It is exactly the right thing to say to a colony of monkeys, and it is the first order the new immortal gives.