If it's going to cost you 50% of a new bike to bring up the old bike to 100% functional, then I'd start looking for a new bike, jmho. Especially since you are looking for a possible, "switch" in style. If your really happy with the Trek, then go for the rebuild and enjoy. I went from a "MTB, converted" to a hybrid to a new Jamis Coda Sport, "flat bar" road bike and I've very happy with the "style change", YMMV.