1998 Ford Windstar Loses forward gears, rough shifting down

Van does this every so often, I have looked into the fluid and its fine, the pan is seeping a little fluid, haven't gone as far as dropping it and replacing the filter. But occasionally the van will be at a stop and it just refuses to go forward, but if I bring the rpms up to 2000 or 3000 it will slowly move until the van will jerk the tires will chirp and off it will continue, this problem only happens occasionally like I said, now the second part of the issue is its hesitation while down shifting from 2nd to 1st it feels like its trying to take off again.

heres more info I can give you :
Abs light is on but that has been traced to sticking rear brake shoes

Check engine is on but is throwing code(s)
1537
1538
which are not related to the tranny

VSS is off its reading 5mph over current speed
confirmed by roadside speed sign and a helpful officer with certified spedo =)

Van is a 3.8ltr with the joyous AXOD transmission, message on dealership inspection paper @136000 (before I bought it ) "tranny pan and servo leaking"

would the correct path be to replace filter and fluid and possibly the seal on the servo?