Yes you can replace your SSD with a 1tb model. However make sure you purchase one that is designed to work with that model as apple designed a proprietary connector for that model.
I would recommend purchasing a SSD made by OWC, you can purchase it on iFixit [product|IF123-133-3|here] for the same price the manufacturer sells it for.
[guide|38511|Here is a step by step tutorial to replace the SSD.]