Wow. Thank you guys for the overnight support!
Pito, apparently the current schematic is pretty much what you've posted. I found this very picture too, but my limited knowledge doesn't let me to confirm to be the carbon copy of my current board. Seems real close, though.

I've also got the idea of buffering, but it's probably beyond my current project, time and capabilities.
Thank you fat16lib for information, too.
Having seen the schematics and components you both recommended, though, while I agree that it's everyone's responsibility to decide what one's need to fit his/her purpose as a newbie I still hold a very straightforward unanswered question (definitively unasked

that I believe others might be advantaged as well:
"Which cheap and easy to be handled by software SD module would you guys recommend to start with an Arduino UNO board? Does truly the Adafruit Assembled Data Logging Shield worth those $5
more of the Arduino board itself?"
I might sound cheap, but the Raspberry PI, although a different device, seems to me a better bargain with included SD and pin in/out. Now, shoot on me

[for the records: the SD module has been trashed]