If the psychologist is able to attend the meeting, that may be a plus. Ideally, the IAS is utilized to gather and organize facts and information. Personally, I would purchase the IAS manual, if only to increase your understanding and de-mystify the process.
This
old thread may be of interest, and also the website of the
Acceleration Institute.
Regarding use of FSIQ 131 rather than GAI of 144: page 5 of the IAS form states that the range of scores "Between two and three standard deviations above the mean (130-144)" are assigned the same point value on the IAS form. Therefore, in this particular instance, it does not appear to be of material difference, as to which score is utilized.