Esta will consider it worthwhile in the long run to repair his undersuit as well as his armor, by thread and needle if he cannot obtain another Make Whole to repair the minor magical aspects of his clothing as well.
Meanwhile, he will repair his armor -- with Greater Make Whole it is but a single gesture, should Merrin wish to watch that, and learn again that magic is real -- and wear it over his bare flesh, to abrade it some little bit, and tolerate the cold by willpower. (If he dared think that this little discomfort should count as suffering, any of his superiors in Cheliax would be happy to show him what actual suffering was, should they hear of the thought. Nobody has done this to Esta in some years, but that is because he is past having punishment-earning thoughts like that.)
The two of them do have the option of starting the clock now on Endure Elements and Planetary Adaptation, and hoping that Esta gets those spells again on his next [day], along with Share Language and Tongues and other such needfuls (Esta does not mention Cultural Adaptation). Esta would in any case cast those spells come sunrise, or come nine hours after dawn, if his [god] reached back again; and would then refresh them later in the [day], and then get more spells on the next cycle, and ideally so on indefinitely. If everything works the way it should; which is why Esta was checking their ability to survive the heat, if he doesn't get more spells this planetary day.