OPCs are the easiest cranks to work on, in my opinion. Hardest part will likely be pressing in the bb cups. I use all-thread, some nuts, and huge washers. Good stuff to remember: everything on the right side of the crank is standard threads, and everything on the left side is reverse threads. Also, the crank takes 1/2" pedals. The Park Tool website will cover all of the particulars.

hth