Wow...that's definitely worse than when I broke my Fang, but I think you approach it the same way. Others will chime in, hopefully, and offer what is probably more experienced expertise, but I've done a few repairs msyelf.
You'll need:
- fiberglassing materials: either a simple Bondo polyester resin fiberglassing kit from an auto parts store, Home Depot, or WalMart; separate resin and fiberglass cloth; or you can buy (my preference) epoxy resin from a hobby store and some fiberglass cloth. USE A RESPIRATOR MASK AND GLOVES WHEN HANDLING THIS STUFF
- CA glue / Super glue
- Bondo or other filler
Try your best to CA glue the pieces back together first. You will have to handle it very gently since it will have nothing supporting it until you finish the next two steps.
Then you want to reinforce the inside with fiberglass resin and cloth. Cut different size strips to make sure you can cover it adequately. You're going to want to liberally cover any areas that are cracked with fiberglass to "bridge" the unbroken parts and reinforce the fractures. A layer of resin, a layer of cloth, another layer of resin is probably enough...but add a second layer of cloth and resin if you need to.
Once that has dried for a good while (I'd leave it for a day), you're going to repair the outside with the Bondo. This is easily the most tedious part, because it's going to mean filling, sanding, filling, sanding and then priming and wetsanding and repeating it all again until the damage no longer shows. Which means you can say goodbye to most or all of your current paint job.
I can't tell from the photo if you also cracked the dome in the front. If you did, I'd actually be tempted to reinforce the inside so it can't be damaged further, but leave the outside crack. It might look kinda cool if you layer the silver and outer paint right so it looks like a battle scar instead of an "oopsie".
That's just a few hints. There are much more knowledgeable sources here, but this method worked for me and your bucket looks repairable.
Good luck!
Chris