Do I really need Desoldering for replacing resistors/caps?

Thank you czarivey.  The link you provided is does't work.  So it is not a good idea to use the old solder that left on circuit board after remove resistor?  

Thank you very much czarivey. Really appreciated your help Sir.
Eddy

Thank you very much.  Any good solder you recommend?  I have a Kester 66/285.

Thank you very much everyone for good advice.

Thank you very much everyone for many good advice.
Wow, I guess I will have to put a hold on recap, seem like very difficult to me. I guess I can do some resistors with no problem. 
Do I search for "Audio repair" online for a good qualify LOCAL tech do to recap for me or should I use any other words. I don’t really want to ship it to somewhere else if I don’t have to and also I can ask him if I can watch him while he do the job and can learn from him.

Thank you very much for your advise.  

Thank you terry9 and Jim.