What's with Linux Mint v13 updates?

On Pentium4 XP laptop I dual boot Linux Mint. Lovely system but I don't use it often since it can't print and excel substitutes aren't very good.
When I do use it, I try updates.
In December, update screen couldn't download all indexes, packages.medibuntu.org... invalid signatures.
Similar today.
But then there was update. 161 of them. I allowed all, since I'm clueless.
It asked whether I want to keep or update /etc/grub.d/10-linux... . Now that one is important for booting!
How do I know? I want to be able to dual boot, and have no idea if to overwrite. I decided to KEEP what I have. I think I allowed it to overwrite in December - fuzzy notes
Then the screen said that everything got installed. But there's red x over the packages icon, and some error display.
Why is Linux so difficult? Is it only for super-duper experts?

I have few screenshots just transferred to windows, in case anyone needs to see them to help me deal with it in the future.

 

Hi act8192,

From Medibuntu Wikipedia webpage:

-- Tom

 

Thanks.
That got me reading a ton of threads about how to fix this. Every one has a different solution of complicated commands and at this point I have no idea which solution, if any, to use on Mint13.

Also can you answer my question about keep or replace grub message?

 

In a terminal type "sudo gedit" (or your favorite text editor), then load /etc/apt/sources.list and delete or put an # before the line about medibuntu.
Save, exit gedit and do "sudo apt-get update", then "sudo apt-get upgrade" then "sudo apt-get dist-upgrade".

Let it overwrite the file.
Grub will run an update anyway so don't be worry about grub's config.

 

Thank you very much, fblais.
It worked as far as I can tell.
It was an adventure for me because I had to exit terminal and reboot after every command which seemed to have crashed at the end. It turns out that I didn't know about case sensitive answer to "do you want to ... Y/n". So "y" didn't work and I was lost. And you may laugh as hard as you want

I'm actually surprised that with the mess I made when those commands ran, the computer is still intact, index error seems to have vanished and yumi/grub dual boot of XP or Mint 13 work just fine.

 

Why?

That is very strange, I thought the capital letter simply meant that that letter would be the default answer if you simply pressed enter.