So my misfire has finally been diagnosed to a bad head gasket and engine mounts. (yes both combined has caused the horrendous idle that has plagued me for quite some time).

I guess it took 5 different mechanics to finally tell me what the damn problem was

Well anyway....He said the current problems with the car are that the water pump is leaking, head gasket is causing compression loss on leakdown test and the mounts are shot.
I can't afford $1500 to pay for the head gasket which I was quoted...

1) Water Pump -- Should I stick with OEM for the pump?

2) Head Gasket --
---a) Is this DIY'able?
---b) Any special tools required?
---c) Should the head need reconditioning at 87k miles??
---d) How can I tell if the timing chain is okay? I would assume its fine at 87k miles.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k