If you are thinking of staying with gas and only having it for a new HWS. A lower cost option to consider?
You are going to need to pay for a gas fitter to install the new HWS. One of our urban family did this several years back as the best option. For a small extra cost at the same time the gas fitter disconnected the town NG gas and installed a connection point for a gas bottle 36kg, instead. Just be sure to purchase an LPG version HWS.
It is worth comparing the cost of the two options. We run our HWS in one property on town gas and another on bottles. We use just over two 36kg bottles a year. The saving in the first year paid for the gas fitter. The daily service charge in Brisbane adds around $300pa to the gas bill for zero usage. Our last 36kg bottle cost $142 delivered and swapped by the truck driver. We use a 9kg swap and go, the BBQ spare when the 36kg runs empty, via a changeover tap. Or you can have two large 36kg, Which would add $30 in our area pa for the bottle hire.
If you have a gas cooktop they can be changed over to LPG by replacing the jets, one per burner. They are the size of a cig butt and a regular spare part, you can purchase yourself. The change should take less than 30 mins. Make good use of the gold plated gas fitter.
Doing the same for an oven may not be so cost effective. It may need the oven removed for access, at which point for older ovens the whole burner may require replacement. A $200-300 job all up.