OP: your second printer sounds like it is simply the connector for you heating element, the connector they use is crap, it is loose and continuity can be hit or miss, it doesn't seem to be rated for the 3amps that the heater pulls and gets hot to the touch. I replaced mine with a deans connector, you can get a good connector from your local rc hobby shop, anything they use for rc is way overkill, thus perfect.
I purchased mine for prototyping and is great for that purpose. I haven't found much outside of printer part that aren't novelty. Use your imagination and model what ever your heart desires.
If you're not experienced with 3d modeling, I would suggest autoCAD inventor, it's free, it's powerful, and has the beginner in mind. CAD is not simple to learn but inventor has a lot of videos to aid you with the basics. Once you know the basics you can draw anything you just may not know the short cuts yet.