1998 Lance 945

Alright, since no one has bitten, I'll bite. It really depends on the condition of your wood frame, 18 year old camper. Basically, your 945L is not worth the cash outlay to replace all the windows. Your best bet is to sell the 945L and buy a new, 4 season model of choice.
I have tried to keep up with my puny little Lance 165-s (no air conditioner needed), which has approaching no insulation and certainly no thermal pane windows, by upgrading relatively low cost items that would make a difference, like block foam insulation where applicable, 200W solar, new converter, battery, and all LED lighting plus a 2K Honda generator.
Since you live in FL, maybe just a Honda 2K for air conditioning (if you have the Cub A.C.) while in the boonies would help. But, no I don't think it's worth renovating all your windows. The only caveat is if you have a terrific TC craftsman near you who will work for a lower wage. Good luck with that.
jefe
At least you won't have to worry about thermal pane windows keeping the heat out in this kind of weather:

Replacing the windows isn't that difficult IF you can find thermal pane replacements in the same size. And I suspect it's possible since camper manufacturers dont make all their own custom hardware, they buy it from suppliers.
I'd start searching camper parts suppliers and see if you can find them.
Buying a new camper is an easy solution... if you can swallow the price!
I do agree it's probably not worth doing though.

If you just want some improvement, tint the windows to reduce the sun impact and use reflectix cut to fit at night and during the hottest part of the day.

You can buy both at stores like Home Depot and do it yourself.

Storm windows are another option.

I have used plexiglas to make storm windows and it works well and fairly cheap.I'am about to build a cold weather camper for skiing and other things expedition style.(Built one before) Got some windows from a place in Summerland BC They custom build them. Think the average camper windows add up to about $1200 cdn with out shipping.
Their website is http://www.sunviewindustries.ca/ I know there are some stateside as well.