Thanks for the nice words!
It is an easy DIY. Just Open the left side wiper and it's shield. A black plastic shield covering the fresh air flap will be revealed that can easily be removed. Once removed, the fresh air inlet become accessible. Just pull the flap within the air inlet all the way to the top and put any used key under it giving support through the air inlet housing. Thoroughly clean the housing and flap with wet cloth. Take some double-tape (preferably 3M) and apply on top of the gap between the housing and flap to completely seal it. Put everything back and you are done with it.
Regarding the automatic fan, if your electrician has not made any "jugaar", you just have to remove a small fuse adjacent to the radiator to make it automatic. Yes, before doing that, get the leakage problem sorted out and install thermostat valve.