Alright I hear you. From what I've seen on various sites where I live the D5100 goes for around 2000-3000 Sek (swedish currency), which honestly ins't too bad.
Besides that I can probably find a d7000 pretty easily for about 3000-3500 Sek, which IMHO can be worth it from the sounds of it.
If you can sell for close to 3,000, and buy for 3,500. Then it would be worth it. The D7000 will open up loads of older but very good Nikon AF lenses that need a body focus motor.