Hate to tell you the bad news, but it is not worth fixing.
It will cost you more to fix that, than it will cost to buy a new one.
Also Stanley does not sell that model or any rotating lasers anymore, but there are a lot for sale on the web. Amazon has then for $153, and there are other places cheaper.
The reason Stanley does not sell them anymore, is that CST Berger/David White made the rotating lasers for Stanley. Stanley Works sold CST/David White to Bosch last year.
Forgot to add:
If you want to try and fix it yourself, the part you need is "Z58-6304-LO" Diode Body Assembly. But this part will probably cost more than a new laser.
Also if you go to the CST Berger site, click on "self support", type in "SP5" in the search box, and it will pop up the parts diagram and manual for your model.