First off sell the accessories separately, except toss in a half dozen mags with the rifle, other wise you end up nearly giving away the accessories.
Second really need to get it fixed or take a loss - would send to one of the guys, with Ghillie being fast and at least check it out.
Third maybe offer it for sale here first, possible already at Ghillie ready for conversions ;-)
HK91 Questions and Answers that I see:
1: Is the gun NIB - Answer is No
2: Is the gun nearly new or mint - Answer is no (i.e. is well used with +4 rollers and has been refinished)
3: Is the gun functional? Answer appears to be yes, the HK91 goes bang, ejects brass and the bullets go nominally down range.
4: What is the bolt gap? - Answer nominally ok but low with +4 rollers
5: Are there any issues - Answer maybe see link on ejection pattern.
Other questions are condition of the bore, group size, how does the bolt look etc.
Should sell nicely as a host gun for a sear (which it probably was) or a project gun (i.e. make a great G3K with a new RCM barrel pressed in would allow the bolt gap to be adjusted), however, not at the $2500+ price of a NIB HK91 nor at the $2K price of a nice HK91 (note my prices are what I have seen locally the GB prices maybe higher ;-). With possible issues, one would really want to see some discount for the unknown plus the nominal cost of repairs, will not guess at a price, since could make a nice G3K host ;-), other to say it might be closer to a grand than two grand (the new SAR8s were $799 and just got a nice HK911 which the original owner had had brought up to HK91 specification for under $1500).
Thus you should either send it off to be fixed or expect to sell at fairly good discount as the buyer does not know what needs to be done (i.e. nearly worst case but probably not if one is lucky, would need a new barrel, trunnion, bolt, refinish plus work for near a grand).