You can DIY that, but you will need a good manual. Figure two days (a weekend) of work for disassembly and reassembly. I rented an engine hoist since I worked alone and left the intake manifold attached.
Would I do it myself again? No, just because of the time involved.

Also, I would really, really convince myself that the headgasket had blown. If it's bad enough to cause low-compression misfires, I would think you've got other symptoms as well (exhaust & oil in coolant, coolant on plug, oil leaking out). 87K does sound low, but the age may have played a role too.

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Prost!