You might as well flush out the cooling system since you will have to take the rad out anyway (see 700/900 FAQ for excellent info on this). This would also be a good time to check your cooling system hoses and replace any suspect ones. There are two small hoses near the oil filter housing that tend to go soft from oil contamination. An empty cooling system helps in the changing of these two hoses. Also, go ahead and replace the thermostat for $10 and 10 minutes of your time.

I switched to Havoline DexCool last year. My mechanic (works at dealer) sez that the DexCool is as good if not better than the Volvo coolant, is cheaper, and much more readily available. Again, there is a wealth of info on the 700/900 FAQ on this subject.

The OEM plastic rads are fine. Just count on them cracking/leaking after ten years or so. I have heard very mixed reviews of all-metal replacements (some good, some not so good). When my rad gives up the ghost, I will probably replace with OEM plastic.

Also, be sure you have one of the new, green expansion tank caps. The older black/grey ones tended to crack and leak.