If you love the bike and the frame is in good condition upgrade it! As AdelaaR says, you can upgrade things yourself, lots of knowledgeable people in the Bike Mechanics forum.
You can swap parts, but the frame is what really matters. When I bought my 2004 Sirrus, I fell in love with that bike, it felt like it was a part of me. Unfortunately after a few years I noticed a crack in the frame and had it replaced with the current model, which is very different from original. I got used to it, and like it OK, but never got over that white frame. Keep the frame, it's worth it. You will love that bike even more after you put some work into it