How to patch a physically weak system & recommended use of sudo?

[Tim <tyskdisciplin_(_at_)_yahoo_(_dot_)_se>]

Hello
 
1. I have a old computer that is slow and has little memory. But I want to keep it updated with patches. I can't compile these patches on the system but I could do it on another faster system. But how can I later apply the compiled patches to the weak system?
 
2. Alot of you seem to use sudo instead of su - when you want to do something that requires privileges. Why is this? What settings are you using for sudo?
 
Thank you!
 
Tim