Mastercylinder Help 98 Disco ABS

My buddy has a 98 Discovery with some problems: I havent had time to get over and help him with the truck personally.. just verbally
He had the Drivers side front left caliper leaking fluid:
He bought a rebuilt caliper and installed:
after several minutes of pumping/holding/bleeding/tighten/pumping /holding/bleeding he finally got some fluid to come out of the caliper. Problem is.. he has absolutely no pressure on the pedal
I told him this was odd that the master cylinder might have crapped out same time as the caliper.
I told he to gravity bleed all four corners starting at passenger rear. He gravity bled each wheel one at a time and fluid did come out at each wheel for several minutes each. He kept the resevoir topped up also. He still has no pressure in the system. He ordered a rebuilt Mastercylinder and it should arrive Tues. -Wed.
What are the steps for replacement? does it sound like this is a master cylinder problem?
Could someone explain in detail how to replace the mastercylinder...anything special we have to do because it is ABS? How do you prime the mastercylinder? Is this going to be an easy job?

HI when brakes are done on a disco 2 you normally bleed normally then its stuck on to a computor to power bleed the system because of the abs system,not sure how this will help you much as not sure if you can bleed the abs module at home,normally on a standard caliper change just pinch off the rubber hose and bleed each corner as normal hope this helps.