*1.6hdi waterpump leak and o-ring issue*

[Lemonbaguet]

I noticed a leak coming somewhere close to the waterpump and ordered new timing set with new pump, when i took out old pump i saw there was a seal right there on the pipe where the rotor spins and it was busted..so how to change the o-ring on the inside of the waterpump housing of the 1.6hdi? Do i need to take out the pipe from the back of the engine that goes in to the housing or can it be done from the inside of the pump housing and just put it in place? Or can i use corteco silicon gasket sealant on it from the inside of the housing side? Cant find anything online about this issue , seems like a hell of a work to remove the pipe

[Lemonbaguet]

There was also on top of that o-ring, somekind of another ring that i dont see in the illustration picture, it was kind of some sort of plastic or hard paper idk..