For vocals: microphone -> xlr cable -> Tascam mic preamp
For keyboard: 1/4" outs (L & R) -> Tascam Line inputs (L & R)------you may be able to record MIDI & Line outputs at the same time, depending on your keyboard
The Tascam comes with Cubase 4le which would be more than adequate.
No offense, but here in the US the big box music store salesman are not going know jack shit about an interface, other than some line of BS to get you to buy.
Just like anything else, the last person you should get information from on making a purchase is the person you are buying from.