To be honest nothing(any type of game) is easy to program. It all depends on your experience and then your knowledge of DBpro syntax. Next add in experience in modeling, texturing, physics modeling, collision, 2d artwork, rendering, handling some type of LOD algorithm, etc... So the answer is different for each person.
Of cousre DB/DBpro definately provides the framework to make your task easier and less daunting , but there are so many variables. You can probably cut you time down, if you have models & textures already designed, as well as some plugins like NG's collision dll.
Is it possible to do a game in the style of NFS Underground? Yes
Will it be as good or as in depth? depends but probably not if you plan on doing everything yourself and your startin from scratch.
take a look at some of the racer's that have been released in both the Program Announcement board, and the WIP board.
~zen