I can't tell you what the difference will be necessarily. I do know my '05 had a stage 1 exhaust on it when I bought it. The exhaust looked the same as stock pipes, but it had Victory Performance etched in it.They had a nice mellow rumble,but not too loud.
The only other thing that I know of could be stage 1 is the air filter and air box cover.
If you are lucky, hopefully the PO removed that restrictive stock airbox and added an aftermarket one. That was the first thing I did was cut the airbox out and install a S&S Airbox. Money well spent.
Then I pulled the Stage 1 pipes and got aftermarket pipes. Those two mod's woke my bike right up. Now I know that Canada has strict noise laws from what Ive read on these forums, so you may have to stick with stock or stage 1 pipes.
Can you post a pic of the bike?Maybe a link to the ad where you found it?Then people could look at it and tell you more about what ou have.
'14 Ness XC