Oh, and about the episodes, no, you don't need to watch all 600 episodes. Just watch the main arcs for the action, then maybe a couple of the suspicion cases (aka, the cases where they make you think ____ is a BO member). Won't give away much more, but I'll see if I can come up with a list that's good for watching.
EDIT:
Quoted from Parkur. These should be the ones after 193.
Cases with Black Organization: 54, 118, 128-129, 176-178.
230-231 (which Parkur didn't include) is optional, though it is a suspicion case.
99-102 is probably important if you're ShinRan (which I believe you are). If not, you can skip it. Same for most of the optional ones.
Unfortunately, I forgot the episode numbers for the cellphone case where Ran suspects Conan again, but seeing as it does not relate directly to the plot, you can skip it and come back to it later.
So basically watch: 54, 118, 128-129, 176-178, 205-206, 212-213, 217-218, 238-239, 253-254, 277-278, 284-290, 304, 309-311, 323, 324, 340-341, 345, 358-359, 390-391, 425, 449, 457-458, 462-465, 484-485, 487, 491-504, 507, 511, 568-569, 580-581, 5830585, 624
Optional: 99-102, 107, 188-193 230-231, 521-523, 616-621