Oil Pan Gasket Leaking
 

I have a 1999 Dodge Cummins. It looks like my oil pan gasket may be the cause of an oil leak. Oil is all over on the bottom of the oil pan and dripping off of the bolts. Do I have to pull the motor to replace the oil pan gasket? I have heard this is the only way to get it done.
Any advice on the best way to make sure this is the area that is leaking? I tried to clean up all of the oil off of the motor and pan but it is difficult to determine the source of the leak.
Thanks for the help.