galaxy23auto

Hi all... Im new to the Galaxy, but not to mechanical work...My sister Managed to cook her Galaxy 2.3 Auto, 1999 V reg.. unfortunally to a point of melting two pistons. Anyway, I managed to obtain a replacment engine, so of course its an engine out job. 1 day later and engine and box out... another day later (taking ages as its not my full time job) got all relevent parts swapped from one engine to the other and got the lot back in. Got everything connected back up time for a test drive, and it seems I have a limp mode box, stuck in 3rd. The box was PERFECT before this, even at 120k!! I think its a lucky box judging from what Ive read on here... anyway, I also want to note theres NO management light on the dash either.. Is there a simple reset I can do, or does she REALLY need to goto Dealer / Auto box specialist to be reset? Ive posted new, because It seems the other causes Ive read have happend while the car is in daily use, and not after being all disconnected.. Any help greatly appriciated... I want to get the girl back to my sister... Thanks galaxy23auto