I would never flush an old trans like that especially one that you don't know the entire history of.. i know most shops around here wont even service a transmission that hasn't been serviced by them before if it has over 100,000 miles.. for example, i know some girl who went to firestone with her car after i told her 1000 times don't get the transmission fluid flushed its not a good idea on that car or any car for that matter (in my opinion).. she went there and they told her that they couldn't do it because it was too old.. so she lied and said it was just rebuilt .. then what happened? they believed her.. flushed it.. and the trans wouldn't shift out of first. she filed a claim against them and they had a 3rd party teardown that showed the transmission had been worn down over years and had nothing to do with firestones service under which they believed it was rebuilt.
heres the kicker.. amazingly they gave her a brand new trans for free and a rental car while it was changed. i doubt youll be so lucky. i said they're a bunch of idiots.. if a report came to my shop that said it wasn't the fault of my shop; i would've told her to **** off. :
: anyway, simple fluid change is more than adequate