My gunsmith guru said pretty much the same thing. Either buy a new one and put a bunch of rounds through it or buy a used one and put a bunch of rounds through it and see if it needs anything.
I'm still dreaming of building one from a kit but I think I will be better off learning on a working gun.
I agree with your gunsmith and Bill DeShivs, buy a complete gun learn what makes it work and why.
There's more to building a 1911 then a lot of people realize.
Study the gun, learn the math of the gun then if you want to build one I would say go for it.
However keep in mind that good quality parts, this includes slide and receiver will most likely cost more then a complete gun.