I have just installed a Accusump also, it was very easy to do and it looks great.

In regards to the gauge, I precharged the system until the needle just came off the peg, as the oil entered the cylinder the pressure rose to about 55 #'s.

I have several similar systems on some heavy equipment that require a precharge with dry nitrogen. The main failure with most of these type systems is corrosion on the (air) side that causes the seals to wear.