The plug is indeed in the same location on all 05-09 Saleen superchargers. The oil level is to the bottom of the threads I believe, but please pull up the SC install instructions located in this same section of the forums. You will also find the oil recommendations. If you go with the 5w50 the recommended change interval drops to 5k miles or so.
http://saleenforums.soec.org/showthread.php?t=5422
Follow this procedure, or search for my thread on how to check it without removing anything. It is a PITA either way, but it is possible.
Personally, the best solution to this design's lack of accessibility is the SC dipstick that was designed and is sold by 281 motorsports. I believe you still need to follow the oil change procedure which includes removing the engine coolant crossover that is in the way the first time, but after that it is as easy as checking your engine oil.
I use the Ford Racing Supercharger oil in mine. It is easy to get and meets the specs.