The hardest part is finding out what kind of plastic it is...could be ABS, but many things are being made from hi-density polyethylene (HDPE). Once you know they kind of plastic you have just get the correct filler rod for your HF plastic welder.
I was able to repair the liner for the propane compartment on the Lance using JB Weld plastic bonder (not plastic welder), it's the only adhesive on the market that will bond to HDPE. I would invest in a welder for what you're looking to do, it sounds like a crapload of work....