In Japan, we hear something like this:
"I'm going to have my house reformed."
I hear it is incorrect and that it should
be "I'm going to have my house remodeled."
Is that right?
Also, by 'remodeling', do we completely
get rid of the old house and build a new one,
or do we (partly) modify the old house, or
does that mean either?
'Reformed' is wrong. It depends how much work. You could have it redecorated, or remodelled. If it's old and in bad condition, you could have it renovated. If you get rid of the old, then that's a tear-down.