Road Wheel on Hardtail MB (Trek 4900)?

I own a Trek 4900 2006 model with disc brakes. Although the current wheels are ideal for mountain biking, I'm starting to enjoy cross country biking a bit more and was wondering if I could buy an extra set of road wheels on ebay or something to swap out when I'm not off roading. Heres a few questions... show more I own a Trek 4900 2006 model with disc brakes. Although the current wheels are ideal for mountain biking, I'm starting to enjoy cross country biking a bit more and was wondering if I could buy an extra set of road wheels on ebay or something to swap out when I'm not off roading. Heres a few questions seeking professional advice.
1. How much would it reasonably cost me?
2. Is it difficult to swap tires with disc brakes?
3. Could I do it by myself with the basic tools quickly?
4. Would the heavier MB frame cause the tires to deflate quicker?
5. Would I have to adjust the brakes and gears when I change tires or can I just swap out the wheels and be good to go?
6. Is there really a big difference?
Thanks for any response.
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