so buddy all things depends on is this your new car?? mean you bought it now??
if yes. THEN
dont replace throttle body, just clean it, ithnik HONDA charge 3k for throttle body and other mechanics will hardly charge 500 for that, clean it you will feel the diff
NGK are good for 20 to 25k, (but if its your new car you never know how much they have done), so recommended that change them, (in my view 200-250rs will be per plug).
coolant upto you, as im not using any coolant in my car and i never feel that i can use it, so i cant guide you in this.
never mess with ecu, fuel economy can also be increased by the above work done..
fuel tank isnt necessary, bt if you can done it that will be good...
if you are using your car from some time, then you might have idea when to change/do that work
any thing you more like to ask more wellcome, or you didnt get my ans you are more wellcome to ask, and the prices mentioned are of my view...