You can't just go, "Ok, I'm gonna make a skateboarding game... I'll just post on the forums and get code off of them..."
I know it sounds harsh, but that's what you appear to be doing...
You need to get the basic engine working b4 you even begin to think about stuff like the skateboard or the levels or anything...
Make sure you post code, of what you have got so far, then ask, Ok, I'm having trouble with making the skater do jumps etc... then you'll get answers, otherswise... Just don't post...
Give it a go, then come back when you hit a wall, don't just try and "make" a game in a few days, it's just not possible...
The one that you saw was probably made by an experienced coder, and over a long period of time...
Again, I know it sounds harsh, but that's the reality of it, you HAVE to have a go at it first, otherwise people aren't going to be willin to help you...

Team EOD :: Programmer/Logical Engineer/All-Round Nice Guy