What were the US Advisers in Vietnam composed of (pre-1964)?

I know that the United States sent many military advisers to support South Vietnam prior to 1964, under MACG and MACV.

I know their approximate strength, and that there were many soldiers attacked to ARVN battalions to help train South Vietnamese soldiers.

However, what I'm looking for is information on just how many of these men were doing what, at various times, and what other military support the US was giving to South Vietnam prior to the Gulf of Tonkin incident.

For example, how many US soldiers were in Vietnam training ARVN soldiers in the field? How many were conducting operations on their own (if any)? How many were technical advisers, teaching South Vietnamese how to maintain or operate special equipment? How many American aircraft and their operations and support personnel were based in Vietnam? Artillery? How many personnel were in a staff role, coordinating the activities of these American personnel?

I guess the key date would be Kennedy's assassination, but other dates are good, too. I really just want to know the extent of American military support for South Vietnam prior to our sending in large numbers of combat troops and the war escalating.