Just for a quick $.02 on the OBA thing..
For my pressure swtich, I just robbed one off a junk compressor. It was cheaper to pick up a used compressor off CL than it was to buy a new switch (at that time).
Ebay or industrial equipment dealers are good places to look for cheap oilers. Cheab being ~$20-30 for an industrial unit. But the reality is that you can get away with just dumping some air tool oil in the intake prior to every use. Heck, the S-10 gus (low riders running bags) run this style of compressor without any oil in them. They tend to last quite a while like that.
Make sure you have a decent length of hard metal line coming off the discharge side of the compressor. The pressurized air that's coming out of the compressor is warm enough to cause the regular air hose to self destruct fairly quickly. In my case, I was having a hose blow out every 8 months or so until I corrected the issue by adding a longer metal line off of the back of the compressor.
Hope that helps!