I don't think any of Acer budget laptops can have docking station (real one). Check whether you have ExpressCard slot on your laptop (similar to one where you put SD flash memory, but wider and deeper). In that case, you might look around for external ExpressCard-based wideocard.
Or, better yet - get a new laptop. You can get GeForce 540M-based laptop for less than $700 these days.
No you can not upgrade the GPU in this laptop. You can however up grade the RAM. About 98% of all the laptops you cannot upgrade the GPU's. Only high end and gaming ones. Sorry for the bad news and good luck.