Hello, every customization expert in the 1/6 world~

I'm a newbie in the 1/6 and I have never customized a figure until now. I have been fed up with the Medicom Trinity figure myself ever since I bought for a wrongfully spent price. The figure itself has really nice head sculp and clothes but lack any kinda articulation. So I have been thinking about switching the head to a new female host but don't know how to do it?

Anyone with some advice to help this soldier lost in the field of customization would be greatly appreciated! Thanky you for reading this message.