Yes you do have to taxi forever, sorry. And then - most likely, be driven in an airport bus circles around the airport to the domestic terminal, from where you can catch the inter terminal bus. Or step out and get a prepaid cab (available in the arrivals area), brave heavy traffic all the way to the international terminal. Your choice. Personally I'd take the inter terminal coach.

If you don't want to arrive in the dead of night - there's a daytime arrival into India - lufthansa MUC-DEL. That might work better for you, connections wise.