It's a good idea to draw yourself a picture of which spark plug goes to which coil terminal and keep it for future reference. Be careful pulling the leads off as they can break easy, pull them by the thick part right near the spark plugs. You need to use a socket set with the proper spark plug socket and don't over tighten. I used a torque wrench to do my plugs up on my ecotech.
Given the coolant is a bit rusty you might want to use a radiator flush fluid before you drop the coolant. Engine block drain plugs from memory are not so easy to get out you can disconnect the heater hoses and flush it all out with a hose and refill the system with clean water and let it circulate for a while and when cool empty again and reflush. If it's still dirty do it again.
When you add the new coolant firstly make sure you have got at least 5 litres of water out of the system and add the concentrate then top it up. Remember to bleed the system properly. I use the Nulon Long Life Coolant as it is a quality product, says it lasts longer and you don't need to use the pellets unless a minor leak shows up afterwards. Coolant shoudl be around 50% to a max of 60%.
