I've got this job on one of these coming up in about a week
. If it is the head gasket and if you have been competent with your repairs so far then yes, this is a good diy'er job. Go ahead and purchase the locking tool for the flywheel and use it if you decide to do the job. Makes the job a lot easier in my opinion. .
I have seen a rear main seal leak after having run the vehicle a little warmer than usual.
Sounds like time to get under there and look around.