Are these authentic original garands still in surplus from WW2?
The CMP M1 rifles come from the entire production range of 1937 through 1957.
How can you know how worn out it is before you buy it?
Any rifle you get from the CMP will be functional or they will make it right. The CMP grading system tells you the wear factors on the barrel and what your chances of good finish on the metal is. Read the CMP's grading system. It's on their website.
Could it still be used in self defense situations?
Any rifle can be used for self defense. The choice of a defense weapon is purely subjective depending on a lot of factors. Whether the M1 is the best choice for you in your situations where you live is another question entirely.
I basically only want to buy one if it is good to go when I slap a clip in.
Any rifle you buy from the CMP will need to be dis-assembled, fully cleaned, re-oiled and re-lubed (GREASE !!!), and re-assembled. This is pretty much a necessity, not an option. These rifles have been in warehouse storage for anywhere from 20 to 50 years. To not do the preliminary maintenence before using (ESPECIALLY if you foresee it as a defense weapon.) is purely foolish....
What model of garand are they? Only M1?
The vast majority of M1 rifles are the basic infantry model. The -C and -D model sniper rifles are available (MUCH higher prices.). See the CMP website for offerings, gradings, prices.
DO any of them have folding stocks?
The M1 rifle never had a folding stock, exepting for purely "one off" experimental factory models.
What is the loading and unloading action?
Huh??? You load an en-bloc clip with 8 rounds, pull the trigger 8 times, and repeat....
Does anyone know if any manufacturer creates garands or garand clones today?
SA Inc. (Commercial) until recently sold "new" M1's made from newly made commercial receiver, barrel, and wood. The remaining parts were old, used, and re-finished to look new GI parts. Good rifles... but HIGHLY overpriced. They are no longer in production as the supply of old parts dried up in the quantities necessary to maintain a production.
Best of luck,
Swampy
Garands forever