I agree it's a good deal not so much a steal - also confused on the shoulder injury is it the shoulder bag you are concerned with? The camera hanging with the neck strap? For the latter I think you can get hand grips for the K100D (not sure on the K1000) and for the camera bags that as so many options other than a shoulder case (everything formal belt attachments , hand carry ons with rollers and a handle) you should be fine there.
Also showing your purchase price to potential client may be an issue
You may make a few sheckles on it , however it is only worth what someone else is willing to pay. Good luck !