the only thing with welding plastic is it is WAY to easy to mess it up LOL.
When I worked at the tool rental here in town, the bossman had me stitch up a rentacan that had gotten a big crack in the outer wall, and it was looking good till I went too far with it. Turned a nice job into an ugly one quick. So, do take the time to get practiced up before working on your baby. :3
There was a crack in my sleds hood on the side near the hood latch band, and my guy repaired with with an aluminum plate and rivets. Came out tight and clean. Not sure if you can do that in the area thats broken on yours. You should be able to mend it with the welding kit. Good luck, and do show us the results!