The spring gets loaded when you lower the roof so it can help with raising. So if you take the lift apart, be sure the roof is supported all the way up.
The central seam is not neccessarily a candidate for a leak. But any vents and the trim pieces along the roof edges are. And if there is some water intrusion inside the roof, you can end up with little pinhole leaks from contact corrosion with the staples that hold the frame together. At 28 years, everything is possible. There is no simple answer, it depends on how much effort and money you want to spend. The guy that restored the old Palomino I mentioned had a complete new roof made from fiberglass. Another friend has patched the roof up as well as he could and covered it with some sort of bed liner.