If the Gun shop will let you at least take it out of the stock, look on the lower right receiver leg below the wood line. There will be series of numbers called a Drawing Number. For Winchesgters it will be either D28291-2 or D28291WIN-13. If there are any other Dash Numnbers(-12, -5) walk away. It's a welded receiver. There were many fewer WIN-13 guns made, and I wouldn't mind having one.
Without taking it out of the stock, pull the op rod back and lock it back. See if there are numbers that can be read on the barrel. If visible, there should be a Drawing number, including letters of who made it(SA, HRA, etc), and a date when the barrel was made. More than likely the barrel will be a post war replacement. Since Garands can only be cleaned from the muzzle, and the jointed steel cleaning rods were hard on barrels, muzzle often get worn. There are gauges to determine this. But, new, excellent quality, commercially made Garand barrels are available, with a cost between $200 and $300. It takes about 30 minutes to install a Garand barrel, so it's not real hard to do if one knows what they are doing.
Stocks can be easily cleaned up. I know a lot of people want the original, battlefield look, but I prefer my stocks to look relatively nice. The easiest way I've found to clean up a Garand stock set, is to stick it in the dishwasher. Removes all the old ;dirty, oils, and grime. Plus, it steams most of the dents and ding out. Unfortunately it won't do much for gouges, and missing wood. But, a Garand purist, or enthusiast, will scream bloody murder if one mentions that. Then wipe n a couple of coats of Raw Linseed Oil(Flaxseed oil ion the supper market is the same tbhiung), Boiled Linseed Oil, or Teak Oil.