My 2012 G37 is due (according to the dealer) for a coolant flush and replacement of the plugs. I looked both up online, plugs look pretty straightforward and the flush didn't look too bad. However I've been reading a bit about it and trying to figure out what "gotcha" parts I should get to avoid last minute problems (e.g. the washer around the drain plugs, etc). I also stumbled across people mentioning replacing the thermostat and hoses due to age/mileage. Is that something that should absolutely be done as long as the system is drained, or are those parts not necessarily due to fail? If so, what are the parts to replace?