Clutch cable or transmission problems?

[4barrel]

I was going through the gears earlier today shifting at 4,000 rpm's. As I came out of fourth, fifth didn't exist...period. I pulled the car over and checked it out. The shifter wouldnt go over at all to even start into fifth or reverse. With the key off and a little playing, it will sometimes go into fifth and reverse, and sometimes it won't. But it will not go into either of those two when the car is started. Some guys told me that the clutch cable is probably stretched. Some others have told me the transmission is out. What do you guys think? What can I do?