If the Contractor has a responsibility toward this thing still, then I would let him carry it out. (Providing your place isnt signed over to you yet, or, you have stipulations in your agreement, that you have a certain amount of time for "things" to be corrected by the Contractor in a timely fashion).
If not, then its up to YOU what you are capable of... We really have no idea of that. (If it was up to me, I would do this, because I am willing to try anything, just to have the experience, and if I goof, can cover my mistakes, you, I dont know personally, so, I cant give you an estimate one way or another).
What I would do, is locate the power source, (breaker) and turn it off. (Have one of those lights (300-500 watts) that sit on the floor, and looks like it sits on a C-clamp, you can buy from Sears or some place so you can get an extension cord to plug it in elsewhere and shine it on the spot).
Then mark all the wires, so you know which one they go to, when hooking them up again. (You can get tabs from your electrical supply store, or get some scotch tape and bits of paper and wrap them around the cords...maybe even make a diagram?).
Ok, now is this close to a joists?
After breaking out the "tabs", and pulling the wires through and securing them...(if from the back, make sure you get the proper clamps, to secure the wires {Sorry, my mind, I forget what they are called at this time..sheesh}), then secure the box to the joist.
If you have to "break" some pieces of plaster while doing this, so be it, you can always use spackling, or hot mix joint compound to patch it up quickly.
Then, take your light an attach it up to your mounting screws for the box. If the mounting screws are "too short", (and I have run into this), then go to the hardware store and get some longer ones
. Make sure you put some washers on the bottom of those screws, to ensure that they will not slip through the holes in the lamp.
If the hole is not anywhere near a joist, then let the Contractor do the job, as you will be busting out a lot of plaster and he will know how to replace it. Also, I would have him install a bracket for a "ceiling fan", so that you can put one in, in the future, if necesary
Ok, my long winded speach for today...
Jesse
