So, you actually can change the processor and video chip in that acer model. See here: [link]
You can also get a better GPU in there if you switch out the motherboard with one that came with the optional, faster video chip. I did some research and it looks like the 7741's used the same motherboards as the 7741z's. It depends on what video chip you have on there now as you don't have too many options. As far as I can tell the only board for sale right now with a GPU is the MBPT501001. It has a GPU but I don't know which one... you'll have to ask Acer and ebay sellers
I only ever recommend ghosting drives if the drive you're putting the image onto is the exact same size. Otherwise it takes up too much space on the larger drive and can screw around SSD's.
The Acer Aspire 7741Z-4433 can only accept up to 8GB RAM maximum. See link: [link]
You cannot change the graphics card at all.
To get it faster, I suggest to get a Crucial M4 SSD, 8GB DDR3 RAM @ 1066Mhz (or 1336Mhz and it will downclock). You could get an external graphics card if you plan to sit at a desk, otherwise the Intel Graphics will do you fine.
Next time go for something with a dedicated GPU, either nVidia or AMD. If you plan to digital sculpting it'll help a lot more.
Average decent build: i5+ CPU nVidia or AMD GPU 8GB+ RAM SSD>HDD, but it doesn't really matter all that much.
RAM you could get for like $50. SSD price varies from $100 - 500, however Crucial M4 is one of the better ones.