A 120V fridge will work fine but it works best if you run down the road with a generator providing it power--especially in the summer time. BTW a new RV fridge will run from $1500-$2000, so I would stay with what you got.
It is your decision on what size generator to get ($1000+ of Honda or $100 at Harbor Freight), but I think, if the fridge is a fairly modern one, even a little $100 Harbor Freight genny will work for just the fridge. Noise is the other consideration in a generator. The Honda is quiet and you can get by running it without the neighbors complaining, but that is why it costs to much for so little wattage.
You will want to have batteries but make sure the converter (120V to 12V) is working and has not been stripped out of the unit.
I see the unit has an AC so you might want a generator big enough to run that and the Refrig as you go down the road--I would. That would make me lean to buying the big quiet Honda ($2000) instead of investing in a new refrig.
You should have some fun with the unit and hopefully you will get lots of good advice from this forum to make it into what you want and need in an RV.
Have fun