The body is fine, as much as it can be in the rust belt, 148Mm on it (92Kmiles).
The LPG device is saving money, yes. Break even point is past.
Gasoline costs €1.7/L ($6.89/USgal) after the recent drop due to the world market stabilizing (was €2.1 a few months ago), LPG costs 74 cents/L ($3/USgal). My buddy driving an E-tron said LPG is cheaper than electricity per distance over here. Then again, electricity price is abnormally high at the moment.