Yup the sights are a piece of krap, but you only need to replace them if you are competing (read: repeatability) with them. If you are scoping your M14, save your money for an ARMS# 18.
And if you are really determined to replace them with M1 Garand sights, all you need is the elevation & windage knob. The base, aperture and spring cover will work perfectly fine.
Indexing the barrel is only a 3 minute job with the right tools and vise. Not a big problem.
Enjoy the addiction. Start shopping for some milsurp 7.62mm ammo and maybe a USGI glass stock.
Cheers,
Barney