After planning to build a new rig to be able to play Skyrim and D3 when it comes - I think I might just wait untill jan/feb since alot of new hardware is comming and it seems like Skyrim doesn't require as much of a state of the art PC that I thought.
So do you think my PC will be able to run Skyrim smoothly? (Low/Med settings @ 1920x1080)
I think you should be okay running the game at medium settings at 1920x1080 based on some benchmarks I have seen. I believe you should be able to set AA to 2x. The game is pretty easy to run compared to other current games. I'm guessing you should see minimum frame rates of 25 at worse and an average of around 35.
I don't think having only 3GB of available RAM will affect your gaming experience.
Note that the test rig is using a i5-2500k CPU. The Radeon HD 5750 would fit in between the Geforce GT 240 and the Radeon HD 5770. I haven't seen any benchmarks regarding how CPU dependent the game is, but it should not be very dependent; at least that's my guess. But since a i5-2500k can easily overpower a Q8300, I would say it is very likely you will loose a few frame rates in the game compared to a PC with a Core i5.
The CPU seems to be a limitation in Skyrim based on what level of Shadows you set in game. You can set Shadows to Low, Medium, High, or Ultra. Apparently Skyrim uses the CPU to generate shadows instead of the GPU. Many folks over at the official Bethesda forums are claiming FPS improvements by reducing shadows.
That being said, I've found Low and Medium shadows to create odd/flickering shadows on walls and faces. High looks good though.
So far as RAM goes, 3GB should be plenty. I have 8GB in my system, but in 64bit Windows 7 while playing Skyrim I typically don't go over 2.5GB of RAM in use with Ultra settings.