Thanks guys for the replies.

I can change the thermostat ok myself, unless this is a car that is a pia to get to.

I have the car booked in to see a mechanic today about the engine mount issue. Hopefully will hear back if that is indeed the problem, or it's something else.

As for the tacho issue, I don't have any friends who have Integras so doing a swap isn't an option. I did have a read of the DIY Ignition Control Module (ICM) Replacement. If this is what needs doing, I can handle that as well.