line 1: completo: s.v. Cassell's, "transf." (3)
quo: rel. pron.; its antecedent is the last masc./neut. sing. noun.
line 2: et: "also" (Cassell's, "As adv., also, even")
line 4: in Choreb: a very odd use of in, probably with some sense of CL's in + acc., indicating aim or purpose. Just translate as "by" (as in "called by the name..."). See R.M.L. p. 367 for more on prepositions.
hic: "this"
line 5: quā, adv., s.v. Cassell's.
Achab: "Ahab", genitive.
line 6: Helias: "Elias" = "Elijah". (For this appearing and disappearing initial aspirate, think of English accents that drop initial "h"s, and French (esp. Quebecois) ones that add them. See R.M.L. O.3. Compare Catullus 84.)
quid: sc. agis (common Latin phrase)
line 7: regnorum: i.e., the Bible's Book of Kings.
line 8: hostium: = ostium (R.M.L. 0.3).
que: R.M.L. 0.1
line 10: illi sancti: the monks giving the tours.
singula: neut. pl. as substantive, or sc. loca.
line 12: in primo capite: "in the first bit of the head", i.e., "at the top of the head".
ubi ... igne: parenthetical. The main sentence is Nam in primo capite ipsius uallis ... uideramus etiam et illum locum....
line 14: etiam et: "even too".
line 16: sic ... quemadmodum: I think these go together as correlatives (LSJ "Corresp. with sic, ita, etc., just as, as...."): "And so ... just as ... they began...."
line 17: ceperunt: R.M.L. 0.1.
line 19: in montem = in monte (R.M.L. G.15–16).
line 21: quemadmodum = (probably) simply as.
line 22: que (R.M.L. 0.1; cf. line 8, above).
line 24: qua: possibly CL adv. quā, more probably a singular relative pronoun where there should be a plural: Egeria is thinking of the "days" as a single period.
line 25: Iesu: yes, "Joshua."
line 27: quemadmodum: basic definition in your Cassell's.
line 28: abitationes: the disappearing "h" again.
line 289: parent: < pareo.
