I will preface this by saying I have not seen this particular All In One. Based on experiences doing warranty and repair work on other brands of All In Ones in General there is not much of a upgrade path to them.
Things You can change.
1. Memory up to what the manufacturer supports, Beyond that at Your own risk. Mine has the same 8Gb Limitation. I knew the limitations when I bought it to fit a smallish space and only for Internet and Word Processing use.
2. Hard Drive. IMO bypass anything except a SSD for Speed. Having used all types I now use SSD boot Drives exclusively in the three Desktop and Two Laptops in the house, a Third laptop is IDE AKA PATA interface and not worth finding the rare SSD with that interface. The SSD drives have dropped in price nicely.
3. Display Adapters are built in with few exceptions.
Usually No way to Add anything to them if it can not be plugged into a USB port.
You will likely find that it uses a motherboard that is very similar to a laptop motherboard complete to Hard Drive size, Type of memory used and usually CPU.
One of the clues to the motherboard being more of a laptop type vs a Desktop is the Power supply wattage. From Here
It is a 90 watt. If I had to guess You also have a laptop type optical drive.
Thus the bottom line is You will not get a lot of games to run well on this computer. The Built in video being the main limiting factor. Other than for gaming it seems to be a nice computer.
I hate to be the bearer of bad news, sorry