If it truly has never been in the water, and was made 5 years ago, it's probably fine to dive. It definitely needs to be inspected, but that's easy to do. The first stage likely has no wear, because the seat is not in contact with the orifice when the reg is unpressurized. The 2nd stage might need a new seat, but since it's the LX model, that has a balanced 2nd stage with a lighter spring, and those tend to wear the seat less during storage.
The titan is one of the all time great regulator designs and if you can really get one that has never been used for $100, you should jump on it.
As I mentioned, you need to inspect it, but a full service is very likely not necessary. The o-rings and plastic parts in these regs do not spontaneously wear out or 'dry-rot' in 5 years as long as the reg has been stored in reasonable conditions.
As an example, many service kits sold by the manufacturers probably have o-rings that are more than 5 years old. (from their date of manufacture) Modern synthetic rubber compounds like EPDM have a shelf life far longer than that.
You could send it to Bryan at vdh and ask him to inspect it for you; he's an expert with these regs because they are the same design and parts as the old US divers double hose regulators and conshelfs. I don't think you'll find anyone with more experience than him.
But, if it were mine, I would simply hook it up to a tank, listen for any hissing, submerge the tank, look for bubbles, shut the tank valve off, breathe down the residual air, and keep trying to draw air. If you can't, it means the reg holds vacuum. Then buy or borrow an IP gauge, put it on the LP inflator hose, and turn on the tank. I would bet that it holds IP perfectly and is ready to go.