A nice upgrade.
What is the issue you are concerned about?
Yes, the GTX750 will fit in the only pcie x16 slot on your motherboard.
The GTX750 runs off of slot power only so power is not an issue.
In fact, it takes less power than your GT640 card.
Dimensions are similar.
Yes, PCIe slot is basically all you need for that.
Other concerns would be available power and the physical size of the card to fit in the case. 750Ti are pretty small, but can be two slots thick and full height. I believe that motherboard is commonly found in precision tower, so space shouldn't be a concern.
Double check if the card requires a 6-pin PCIe power connector and check if there is there an available cable coming from the power supply.
The motherboard isn't your concern for fitment*. You need to make sure the case is large enough (since a GT730 is likely a low-profile card, whereas a GTX750Ti is probably full height). Also a GTX750 is probably 2 slots wide.
*750Ti is a 75W TDP card (usually without external power connector), so you need to make sure the (OEM) mobo can supply (standard) 75W through the PCIe x16 slot. For OEM systems (especially small form factor ones), the mobo may be limited to 30-40W over the PCIe x16 slot.