Have developed an itch to build my first AR. are the LMT products like uppers and lowers considered top-tier? Will parts from different manufacturers and vendors be "drop in" fit? Will I need any particular gunsmithing skills? I consider myself a decent mechanic and a pretty good model builder. Can anyone direct me to a site that gives a full breakdown of each & every required part that I would need to buy. Thanks in advance for you input and your help.