All so-called "golden" $1 coins (both Sacagawea and Presidential Portraits) are standard circulation coins worth one dollar. They do not contain any gold and are not rare.
It is called an "appraisal" and can be done by any licensed real estate appraiser in your area. It should incorporate the features of the house, the location, and recent comparable sales in the area.
New Zealand Sixpences were issued in most years from 1933 until 1965. Decimal currency was introduced in 1967. Depending on the year, a circulated Sixpence in good condition might fetch anything from...