Some of the previous posts correctly mentioned that a replacment barrel needs to be indexed properly. Special tools are required to do it on Garands.

Springfield Garands did not have journaling marks on the barrels and the receiver like the 03A3's did, which is why you need a special set of gauges to align the barrel's foreward splines and aft sight base. I think the CMPicon used to sell them but I am not sure if they still do.

The installer has to torque down the barrel in increments each time checking the indexing and if you go past then you have to un-torque the barrel back until the gauges line up. If your gunsmith did not use the proper gauges when he installed the barrel, it would be very difficult if not nigh impossible to have the barrel indexed properly by eye.

As mentioned, if you take it to someone that knows Garands the first thing they can do is set up the gauges to see if the barrel was indexed correctly.

Also, the standard Garandicon cleaning kit consisted of a steel cleaning rod. They were also issued with a plastic barrel guide that most most troops didn't bother with and so after hundereds of cleanings from the muzzle end of the rifle and hundreds of rounds fired, the muzzle wears and the rifling is not as tight. Unless the crown is really beaten up, the muzzle wear usually would have more effect on accuracy, this might be why the guy told you to replace the barrel. It sounds like the barrel indexing is certainly suspect. Sucks that you have to spend more $ to get it corrected.