I noticed that they sell 2 different sized chevrons at the equipment section... Can someone clarify? I'm assuming the smaller ones go on short sleeve.

you are correct, smaller on short sleeve. larger on everything else.

At what point did people buy their uniforms? I remember reading in the patrol guide that your CO inspects your uniform and signs some form or something that you take with you to your promotion ceremony or something, is that your cop uniform or sgt? I know that you get promoted in your dress uniform with no chevrons, did everyone just buy the chevron'ed stuff while in BMOC? This might seem like a stupid question, but I should be in the next class and am planning to buy totally new uniforms, mostly because I haven't really bought anything new since the academy, and wanted to know what the timeline was.

Uniform inspection is done by the academy personnel days before promotion, you have plenty of time. I would purchase my items while in Bmoc.