We dont really have a basics of converting document. Maybe in the future that will be something we have to work on. Making the block was the difficult part for me because I dont have the tools to do the machining. Yes, the oil should be well filtered. I filter mine with a 5 gallon bucket strainer like the ones here:
http://www.dudadiesel.com/search.php?query=strainer+strainersThen filter before the pump with a car filter. Seems to do the job well for me. Yes it should be well filtered, especially with a pressure system. I believe that is one of the benefits of a siphon system, the system can tolerate dirty oil better. I dont think small amounts of gas mixed in would cause a problem, but I think antifreeze can cause problems.
Yes, a drip style would be less picky when it comes to dirty oil, the bad part is regulating the oil flow to get a consistent temp.