2002 Kia Spectra need advice on what to do next

Engine Performance problem
2002 Kia Spectra Automatic 123853 miles

I have recently bought a 2002 kia and I feel that there are two problems with it
1) when I drive I can some what feel the engine and when the car stops at a red light it kind of vibrates ( not to strong to be a real problem but it's kind of anoying

2) I feel like its spends to much car for a four cylinder how can I check if it realy is four and if it is is there anytihing I can di to improve the mpg

thanks for your time and sorry I could dante but I bought car and am 19 therefore I am broke