I have built most of it, just the last few mounted heads and goat horns. When I build them and walk through my house to head towards the back of it, the game freezes! This has happened multiple times now and is very frustrating. And the game disc is in exquisite condition so that isn't the problem. Anyone know how to overcome this problem?

Freezes have been happening frequently for many people in all of the Hearthfire houses, since release. Nobody at Bethesda has officially acknowledged it. It seems to relate to the number of wings built and NPCs living there.

Having Serana from Dawnguard as your follower also seems to raise likelihood of the freeze.