It would be futile to try and "see" if your header gasket is blown, most of the time if it is it's blown right around an exhaust port which will be covered up by the header anyway.
And yes, if you have a broken header bolt, and there is a reasonable possibility that the header does not have close to an even amount of torque for each header bolt, or if you torqued the header bolts out of sequence, than you can have an exhaust leak.
Don't assume that because you have an exhaust leak the header gasket is necessarily bad. If I were in your shoes, I would remove the broken bolt if possible and replace it, and then retorque in the proper sequence. If the exhaust leak doesn't go away, check to make sure the ball/socket connection between the header and midpipe is secure and that you didn't overtighten one of the two nuts on the collector studs or something like that. If you didn't recently install these headers, than this might not be a likely issue.
If after checking these things you still have that lovely "tick tick tick", than you guessed it, it's time for new gaskets.
