Replacing Oil Furnace with Heat Pump
A blower will only work if you are content with A/C only and no heat. It's probably illegal to have a house with no heat unless you live in the tropics. AFAIK, most A/C units cannot be converted to heat pumps, so it would likely be a complete system replacement.

Also, with conventional heat pumps in all but the most temperate climates, you need a source of backup heat because the heat pump will not work well in very cold weather. So you still pretty much need a furnace with a heat pump. Only heat pumps using alternate heat sources such as ground or ground water do not need backup heat. Such systems are more costly to install than backup heat, but should pay off in the long run with better efficiency.