N2spd

I have a speed master lower unit that I need assembled. Anyone know what this might cost to have done. When I bought my boat it had a xr lower unit on it but the guy gave me a shorty speed master lower unit and a imco upper . He thought he had broke something in the lower unit so he took it apart but it ended up being the forward gear in the upper. I'm assuming the upper is no good because it is chewed up from the broke gear/shaft but he said nothing was wrong with the lower unit and gave me a box of of parts. Gears shafts etc. Would it worth putting back together or should I just keep the xr. Thanks.