By all means please bring your computer to a qualified/trusted service shop to have its interior cleaned properly. While there I would recommend asking if its cooling system can be checked.
However, all 11 EPs on a GT 730 is a tall order to fill. I'm afraid you will never get high-end or even medium performance out of a low-end graphics card. That doesn't mean the game can't be played, but the heaviest of the EPs (Pets, Seasons, IP, ITF) will likely be too much for it That card will never run the game at a consistently high fps; vertical sync isn't going to change that, it's going to prevent the card from running away with frame rates which this one isn't really strong enough to do.
The minimum for higher end performance for all EPs within that series of cards on a desktop would be the GTX 750. There's a world of difference between the 730 and the 750 even if by series number they don't sound all that far apart. For higher Graphics Options settings and better performance, then at least a GTX 760.
You cannot compare TS3 to TSM (which has at most one expansion) or TS2 (which was designed in 2003-04 when consumer hardware offerings were very different than five years later) in this regard. TS3 with its open world simulator is miles away more demanding on its hardware, by 2009 standards.
