Digital Download Pricing

I recently took some photos at a fire scene in my area, and received a request from one of the firefighters that appears in a few of my shots. He would like to buy a digital copy so he can have a friend of his, who is a professional photog on the west coast, "do some work on the picture". I talked to a friend of mine locally and he suggested using a commercial release if I decide to allow it, and to 'price accordingly.' My question, of course, comes down to what one should expect to pay for something like this? I know it's a risk allowing the original file to be purchased but as long as it's not resold or claimed as someone else's work I'm OK with that on a limited basis.

I'm a full time firefighter and photography has always been a hobby that I just recently converted to a business. I don't do weddings, portraits, etc. at this point, but I do offer prints/products from events that I cover (fires, airshows, etc.). Long story short my photography isn't my main source of income but I don't want to give anything away. Most 'pricing guides' I've found don't seem to work well for me since they're largely based on how many shoots one wants to do per year. Thanks in advance for any help with this.

Correction; he said full release, not commercial, but added his full release is typically part of his commercial projects (brain fart on my part). After reading the personal release provided by Smug Mug once more, I believe that would be sufficient for what the customer is asking. But I still don't know where to begin on pricing, and that's where I'm looking to the forum for advice, or information on what others charge.