So I tried to do an upgrade.
My first call was to go to Apple store. Asked for the prices and their bits were gold made, since the upgrade was over 400€, wich is more than the computer itself.
More research was done and I found some memory chips from Kingston that were compatible. Amazon sells them for 37€, which is something more realistic.
The instalation was not really difficult. After umplugging the computer, turn it upside down, and open the round base, I was able to see the original chips. By pressing the two retainer clips to the sides, the first chip came out. After doing the same with the second one and I had reach half my journey.
The instalation is just doing the same in the reverse order. Put both chips with a small tilt, press them down so they fit securely and then put the round plate back to the original position.
Piece of cake. There are detailed instructions here.
After that, I restarted the computer, and everything goes fast as a rocket.
To be sure, and since I didn't use the official chips, I ran Rember, a program that do an extensive test on your memory. Everything was fine.
Im proud of myself