[V6-12v] V6 serpentine belt

[Kent McLean]

I'm trying to change the shredding serpenting (accessory)
belt on my V6 '94 100 S Avant.

I've got the cap off the idler pulley.  I tried a 6mm hex
Allen wrench, which didn't work and may have munged the
socket. I then thought it may be a Torx head, so I tried
a 40T head on a ratchet, which fit not-too-snugly, and
turned it clockwise, but it just rounded the points on
the 40T (made by Lisle in USA).

a) What size is the tool is supposed to fit the hole?

b) Is it clockwise to loosen tension on the tensioner
    to remove the belt?

c) worst case, how do you remove the tensioner itself,
    in case it needs to be replaced.

On a positive note, I did replace the O2 sensors yesterday,
and it didn't throw any codes (yet).

Thanks,

Kent McLean
'94 100 S Avant, "Moody"