Upgrading RAM

Just looking for advice/opinion. I bought from ebay, what i thought was an x220 Thinkpad with 8G of RAM..turned out only to have 4. I left a bad review but will keep the machine. I put Arch/Sway anyway.

I want to add RAM...i think it can go up to 16. I looked on line and i think it would be about $50 to buy the memory...so i thought o would find an online tutorial and add the memory myself...is this a bad idea?