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That's a good question, unfortunately, I don't know. I never really used PLA, I just stayed with the natural ABS. I haven't printed any litophanes in years though, so the best practices might have changed since then. If you have pictures of your results, it would be cool to share them if you can.
No, I don't sell them, I just made some for myself, family and friends.
A good/stable printer that can do low resolution prints would work. I think most good recent printers should have no problems printing lithophanes, I personally use a lulzbot mini/TAZ and it's great. But I do work for lulzbot, so my opinion is biased.
I'd suggest you remove the rambo directory from arduino, and install it properly using the new methods available in Arduino. See http://reprap.org/wiki/Rambo_firmware for instructions on how to get it installed. I think that if you installed the arduino addons for 1.0.x that might be why it's not working for you.
Soldering is NOT Rocket Science!
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