We will need the exact model. It will be G6-xxxxaa where x are numbers and a are letters.
This will tell us what you have now. Some models in that series have the processor soldered to the motherboard. All will take at least 8 gigs of RAM and some will take 16 gigs, and all can take a SATA 2.5 inch SSD which might be enough upgrade for you in and of itself.
G6 models all have about the same chassis configuration and memory and hard drive are accessible through a panel on the bottom so the upgrade procedure is not hard.
Processor upgrade, if possible, would be much more involved.
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