engine misfire - P0300

I have a 1999 Chevy Blazer 4.3l, 4wd that suddenly started running very rough and could barely pull itself down the road. Fuel pressure is about 57psi running, and 60psi with the engine shut off. Check engine light came on - P0300 - random cylinder misfire. I have tested the ignition module and it is good. I was going to replace the coil, but can't figure out how to get it out of the bracket - it looks like metal dowels holding it in, but I can't drive them out. The fuel pressure regulator was replaced less than a year ago, but the spider was not replaced at that time. I need to know how to replace the coil, and how to accurately diagnose the spider. Thank you.