The Technician's advice was partly to cover himself and the shop he worked for. He doesn't want you coming back after a week saying that the repair did nothing, and demanding your money back.
Should you have replaced the motherboard? Yes. Most likely, you should have replaced the motherboard with a different integrated video chipset from the one that came with it originally. The HP DV2000/6000/9000 series fiasco comes to mind. If you originally had one with an NVidia chipset, and it failed, although it was possible to replace the motherboard with another of the same... you were better off replacing it with one that had an Intel chipset. With the NVidia chipset boards, you never knew if you were getting a pre-failure board, or a repaired board that might fail again, or one that had been repaired by replacing the parts with ones that weren't defective, or one that was manufactured with non-defective chips.
Point being... the reason why your board needed to be reballed wasn't addressed necessarily with the fix. It was repaired in a manner that saved you money because you chose cheap over best. Did you get a working laptop back? Yes. Did you have to spend as much money as it would have cost to replace the motherboard? No. Do you actually have a reason to complain? No.
If you wanted it fixed right, to where you could use it in any manner you would have liked, you should have replaced the motherboard.