300tdi problems?!?! Head gasket??

hey people,

I aint been on this forum for ages as i sold my defender 90. Anyway im back as i have bought a discovery 300tdi 1995,

Now for the problem?!?
Firstly. After driving the disco home (25miles) i parked it up for the night but woke up to a massive pool of oil, Afetr inspectingeverything i found out the turbo was shagged! So i have today out a new one on and all seemed ok, And it has stopped leaking loads,

But. . After a short run around the block the cooling system is presurizing, So mush it is pooring from the header cap?!?

I still have a pretty bad leak from what seems the rocker cover but im not 100% sure yet!

So my questions are.....

why is the cooling system pressurizing?!?
And why did it mysteriosly dump a loud of oil over night?

am i right in thinking head gasket? Is this an easy fix??