is it better to know how to fix your bike rather than to take it to a shop and let them fix it?? I was wondering if it was better to take some classes to know how to take apart and but pack together and i was wondering if this would be a good investment if im trying to purchase a bike in the future.  

Whether modifying or just maintaining your car or motorcycle, if you are handy with tools and you enjoy doing your own maintenance, if you do your own work you will be better off. To further clarify, let me make it clear this is only applicable if you know what you're doing. Be sure you learn from someone that knows what they're doing or you could find yourself with a dangerous machine! That being said, remember: YOU care more about the condition of your own motorcycle than anyone you pay to do the work. With the money you can potentially save you will be able to afford parts to customize or repair your bike. All that and the pride in doing your own work.
Just remember to check everything you do - 3 TIMES AT LEAST!!!!