I have a supercharged 55 reg range oil gone in water coolant and now every were in engine from bottle top up is it the heads gasket guys ? How much to fix

Hi guys I've just brought my dream car after some one wrote off my BMW. I have a 55 reg 4.and half litre supercharged range rover I believe New battery as other one was dead .I drove it 4 mile home and it started flashing a battery light then all types of lights abs air suspension ect that's...