I need detailed refreshers

[ShadowHM]

Yes, it will.  You'll effectively get a doubled prayer effect along with the mana regen.  Any four-socket polearm-class weapon will do for Insight (yes, the desert mercs can use polearms), although ideally you'll want an ethereal version for the extra damage.
[right][snapback]109703[/snapback][/right]

Don't be afraid to make it in the first four socket polearm class weapon you find (that the mercenary can hold). Eventually, you will have more runes available, and can make an upgrade when you find another suitable base weapon for the rune word.