Totally your call. You know what you like and what you want more than anyone else possibly could.
Here are a few thoughts. We owned a 1999 Coleman - similar vintage to the one you're looking at. While Coleman's were the best-made popups back in that era, they did have some problems. In particular, the roofs. Ours had a one-piece ABS roof that developed problems. The one you're looking at doesn't appear to have the ABS roof, but it's hard to tell because they don't tell what model it is. When Coleman began having to replace the ABS roofs under warrantee they switched to an aluminum roof (I believe). That also developed problems. I think the one you're looking at may have that aluminum roof.
For what it's worth, I sold our 1999 Coleman for $2500 US about a year and a half ago. I think $3500 CA is high for what you're looking at. The only way to find out is to make them a low offer and see if they go for it.
I totally "get" what you are talking about with loving the popup camping experience. There are aspects of it that I miss in our TT. I particularly miss the open, airyness of the popup at night when the owls are calling.
-Speak