No need to drain from the 'block' as you will be removing the lower coolant hose, which will drain the block completely as well as the radiator. The only coolant remaining will be in the cabin heater core - about 1 pint.

Because the coolant is fairly new, you could 'reuse' it so long as the container is clean and there is still enough of it. Use an old Tshirt as a filter when you pour the coolant back in.

Using G-05 is OK. But I would still flush with two gallons of distilled water before pouring in the G-05. BTW, a gallon of VOLVO stuff is not that expensive.

Do not over tighten the radiator hoses. Tighten to the point that you can no longer make the hose turn by twisting it. If you reuse the hoses, ensure the clamp is in the same 'groove' location.

If the thermostat is 'old', replace it.

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Keeping it running is better than buying new