I was wondering, can you replace the ink tube and the tip of a 3000*f with a f-3000 tip and ink tube? i got a 3000*f and the red tip and ink are different than the blue one and so the red cap doesn't fit right.

You should be able to, since they're basically the same pen.

o yea what is the writing on the ink tube of a 3000*f?

Edit: is it either of these?
zebra SK-0.7, 02-02 Japan
Zebra CC 92 10 01

And exactly how long is it?

The 3000*F tips are silver. The writing on the inktubes of mine says ZEBRA SK-0.7 (some Chinese symbol) 02 12 JAPAN. That's what my blue inktube says. The red one replaces the 02 12 with 00 04.

The ink tubes are 9 cm long.