Using Character Creator, along with the Essential Morph pack, it is possible to make quite a range of adjustments to any character.
If you really wish to do the work yourself then ToKoMotion has 2 tutorials outlining some of the steps involved using Character Creator and Sculptris (Free)
Part 1:
Part 2:
Just adding a head created in some other software really won't work with iClone or Character Creator.
Gerry
System: Win 10 Pro (21H2), Asus X99-E WS, CPU i7-5930K -3,5 GHz, 32 GB DDR4 2666-16 RAM, NVidia GTX 1080 Ti GPU - 11 GB VRAM(Driver Studio-536.99), Samsung 850 Pro 512 GB SSD, 6 TB HD storage.