I'm on dial-up and can't dsl, or cable where I live.
Is there a way I can update Mcafee manually, instead of having to wait forever?
You can download VirusScan DAT and engine updates seperately but not the general SecurityCenter updates and patches that go out regularly unfortunately. I know downloads can take ages using dialup as I have experienced it myself in the past and yes your machine will slow down a bit whilst doing the updating, especially if it has a lot going on at the time and its resources are nearer to the minimum system requirements.
There is no other way of updating, sorry.