Is it safe to upgrade my RAM and/or internal HDD?

I have a 13” mid-2012 MacBook Pro model number 9,2. Here are the specs

8GB RAM I had the 4GB in it when I bought it and upgraded it to 8GB because it said it was configurable to that. I see some people running 16GB and i am concerned if I do that and the computer doesn’t accept the RAM or something.

2.5GHz i5 Dual-Core intel processor

500GB of internal HDD storage. I am scared of buying an SSD because i don’t know if the computer is able to use SSDs. I know that there are lots of people who have already put SSDs in their computer but I am still sketchy about it and i would like some fact or something like that that specifically says that my specific MacBook Pro model supports it.

I have installed macOS Sonoma 14.5 on the computer using OCLP and it takes a long time to boot up and a bit for it to get faster and more responsive after I login.

If anybody could help that would be great!