I went to this specialty runner's shop and they measured/scanned and gave me running shoes that are perfect for me. Paid $109 for some Brooks.

First day running in these and my shins hurt and I can't run as far or as fast.

Am I supposed to break them in?

your shins hurt because you have shin splints from running too far in too short a time frame, give yourself some time to adjust

i don't think they're suppose to hurt that bad but when i switched shoes it usually takes me a run or two for them to "break in" but i have fucked up feet super high arches and I've torn my plant fascia before

Yeah give it some time

Could also be from poor form.

Usually shin splints take a lot of pounding. Proper form can help a lot in relieving shin splints especially when recovering or trying to run with them. Some people get them easier than others keep in mind. I do doubt it's the shoes though. I always buy two pairs at the same time to keep them as un worn as possible actually. Worn in shoes actually cause problems like this.