2 days ago I noticed it wouldn't shift into 2nd. Then yesterday it worked fine, but when I was coming off the interstate, it wouldn't shift into second, then 4th. I noticed as I was trying to back out of the parking stall that reverse wont work either.
1st, 3rd and 5th work just fine, it feels like 2nd, 4th and reverse just aren't there anymore. The stick goes back to the neutral position but it feels like the 2nd, 4th and reverse just aren't there. Ive had this car since it was new and its been a great car, I want to get this fixed.

A friend told me its probably the linkage. Where do I look to inspect/fix the linkage?

 

the linkage is between the lever and the selector forks.

 

Sorry for being such a noob, but where would I look to examine the linkage? under the hood? under the stick boot?

 

yes.
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front wheel drive i assume. The adjusters (turn buckles) will likely be under the bonnet, on the top of the gearbox. whether you can see it past the engine, i dont know. Have a look while someone sits in the cab moving the lever.

The bracket under the stick boot is also good to look at.

 

I just had this same problem check to make sure there is fluid in the clutch reservoir. Then maybe your master cylinder went bad thats what mine did New master cylinder was only 30 dollars and about an hourto put in