I've done a LOT of plastic welding (that term used loosely) with a soldering iron. If something is cracked or broken and you have the two pieces that go together perfectly it's quite easy to do with good results. If you have to cut and patch pieces it's harder but still doable. My son and I have used the cheap Harbor Freight welder with decent results but the best ones are when I don't need any additional plastic, just melt the existing plastic and move it around. That said, there a lot of good epoxies out there for automotive use that are amazing.