I have upgraded a Trek 1000 and, like any upgrade, adds a lot to the quality and fun of the bike ride. However, I would not have upgraded it UNLESS I already had the parts and was able to put them on the bike. The upgrades were all quality, used parts from another bike that I took apart when I started buying new old frames and new bike parts. And YES, I got the "itch" to learn to do bike mechanics and build a frame, so I bought an Italian steel frame off of ebay, along with new and used bike parts, and started building. I would not have been able to do it alone, but was able to do it with the help of friends who loved to build bikes and share their knowledge with me. A year and a half later, I upgraded my ebay frame, buying another frame and transferring my good quality parts from my Italian steel frame -- again, doing this with the help of friends. Then I looked around and realized I had enough "spare parts" to build another bike (many from the original Trek 1000), and, you got it, with the help of friends, built another entry-level bike that I sold to someone interested in trying cycling. It felt good to build something for someone. No, I did not make any money on the deal, unless you call earning money on parts just sitting around. Personally, I don't feel used entry-level bikes and bike parts are worth much on resale, but are great to pass along to another entry-level rider!!

So, in a nutshell, I feel that unless you have "extra parts" or someone willing to give or sell cheap good bike parts to you, the Trek 1000 may not be worth upgrading. To save money, maybe a good quality used bike would be worth the upgrade? OR, if possible, find someone who will work with you to build a bike on the frame of your choice. Personally, I found it good to buy a good "trial" frame to build first, putting more money into components than frame, as I began to wrench. Then, once I learned a few things and rode awhile, I was able to watch others, ask questions, and investigate more bike parts and frames, so that when I felt comfortable and more knowledgeable, I was able to find a "dream frame" and transfer the parts worthy of transferring and changing what needed to be changed. It is a lot of fun, very educational as I have learned more and more on every bike I have built, and worth doing -- but YES, buying a whole bike at once is always cheaper!