Even the 95's were build after the ability to service was essentially eliminated. The heat pump AC units in that era were not especially loved by their owners from what I have read.
If you can do all your own installation work, I guess the $150 price is good, but if you have to have someone else put one on, I would think that a new unit is a better deal.
The new Dometic HP on my 2014 is a good unit, heats down to below 30 F vs. the minimum of 35 to 40 of the older HP AC units. But, it is pretty noisy.
I would use the original Argosy AC unit as long as it works well for you, and not replace it at all until you have an actual failure.
If you have the original furnace, it well may be dangerous simply due to combustion chamber rusting. However, a new propane furnace is not dangerous. You can replace the original furnace pretty easily.