Welcome to the madness. That's a great trailer. Has it been used in recent years. There are several in the New England WBCCI Unit. Join the club and come to the Rally's. Contact yukionna
current Presidentis of NE Unit. Lots of help available there, especially for the vintage. I have a 68 Caravel
and 59 Overlander. If you are comfortable with hand tools and things that thread you should be able to handle most jobs. The axle replacement being the exception, some here have done that.
When you say you replaced the floor (ie the plywood) do you mean the floor or the flooring (ie carpet, tile, vinyl)?
Did you remove the appliances, water heater, furnance, or work around them?
Post pictures, it's the best way to get very specific guidance from others.
If you have gas and the lines look ok, find the outside values on the lines and turn them all off. Turn on the gas at the tank and regulator. Go inside and if there is no gas smell in a couple minutes then crawl around under the trailer to check for gas smell. No smell then turn on the line to the stove with the stove and oven off. No smell then turn on a burner until you get a little gas smell to purge the air. Find a site online that explains how to adjust the air / gas mixture and you are ready to make a cup of tea. What kind of heater does it have? A new converter and new battery will likely be on your shopping list.
All this is a lot easier when the temp is above 40.