Questions that you might be able to answer- is memory something that varies computer by computer? (That is- it's a PC- I'm assuming Apple is different). Am I going to have a hard time finding memory that works in a 4 year old computer? Am I better off just forgetting about anything on that computer and waiting until I have the funds to replace it down the line?
By memory you mean RAM, right? If so, then yes there are different types of RAM out there but you shouldn’t have any trouble finding what you need to replace the RAM on a 4 year old computer at all.
What you need to do is find out the type of RAM the motherboard on your computer takes and what the maximum capacity it’ll accept is (It’ll be by the gig). This is usually as simple as finding a user’s manual or heading to the manufacturer’s website to see what sort of RAM they suggest for the model computer you own.
From there, take that information and buy your RAM. The good news is RAM comes cheap these days. Even cheaper if you buy it online from a site like newegg.com (very reputable and reasonable, I literally built a computer with things I bought from that site for a college project). It’s also very, very easy to install on your own to save yourself the cost of paying someone to do it for you. For a laptop it’s usually a matter of a couple of screws and literally “popping out” the old RAM and putting the new sticks in and closing it all back up. Honestly, the hardest part is making sure you get the right RAM and the right amount.
If you need any help tracking down the RAM you’ll need or want to run by what you’re looking to get before you do it, just let me know :)