千里之遙 A Thousand Li Of Thorn
行者看夠多時，將雲頭按下道：「師父，這去處遠哩。」三藏問：「有多少遠？」行者道：「一望無際，似有千里之遙。」三藏大驚道：「怎生是好？」行者看够多时，将云头按下道：「师父，这去处远哩。」三藏问：「有多少远？」行者道：「一望无际，似有千里之遥。」三藏大惊道：「怎生是好？」
逐句解 Line by line
Pilgrim looked his fill for a good while, then pressed his cloud-head down and said, "Master, this place runs a long way."
哩 is fixed at li across the corpus, a throwaway ending of the spoken language, roughly the shrug in "it goes on a fair way, you know". 將 is the disposal marker at jiāng, taking the cloud as its object.
Tripitaka asked, "How far?"
Four characters of Chinese carry the whole question. The unit holds its own attribution and closes its own quotation, so it stands as a segment however short it looks.
Pilgrim said, "As far as the eye reaches there is no end to it. It seems a thousand lǐ off."
一望無際 has already been used of this same view by the narrator, back when Pilgrim first sprang up to look; the phrase returns here in his own mouth.
Tripitaka was greatly alarmed. "What is to be done?"
怎生是好 is a set cry of dismay rather than a real question — closer to "now what?" than to "what shall we do?" — and the English keeps it impersonal.
The exchange is built on a lopsidedness you can count. Pilgrim's report takes nineteen characters and his answer thirteen; Tripitaka's question takes seven and his reaction nine. The disciple explains at length and the master reacts, and the master never needs more than nine characters to do it.
The thousand lǐ is not meant to be exact. It is the standard spoken expression for a distance past reckoning — the same figure that gives the proverb about a journey of a thousand lǐ beginning under the foot — and Pilgrim hedges it with "it seems" in any case. What matters is that the ridge cannot be gone round and cannot be crossed at a stride, which puts the party in the unusual position of facing an obstacle magic does not obviously solve.