Engineering has consistently been described as a gigantic maze where people may get lost for weeks at an end if they forget their compass or breadcrumbs. Curiously STXI was the first piece of Trek to actually show this reality... But TOS did its valiant best, showing a different corner of Engineering in basically every episode. Sure, they tried to claim it was the same set only minimally modified, but we aren't that easily fooled!
On the general issue of Finney preparing... Now that's an odd one, too. Supposedly, Finney's plan could only see action if his name came up in the ion pod duty roster. The list may not have been particularly long, if only high-ranking officers or computer experts were included. But it can't have been too short, either, as it was plausibly argued that Finney's turn during the fateful mission was a completely random one. So, Finney kept his little plan on hot standby through a dozen ion storms? I hope he managed to get fresh water and bisquits to his hideout every now and then...
Perhaps Finney had several plans where he could plausibly blame Kirk for his "death"? Not too many of those, of course, or he'd have risked having his preparations on one or two of them getting uncovered. No wonder he kept his hatred going for years upon years!