The Dell CRT monitor is probably going bad

I've noticed for the past couple of days the Dell CRT monitor is doing this little flicker jumpy thing, like it jumps back and forth vertically like a couple scan lines. It doesn't happen when it's first turned on. It is about 6 or 7 years old by now (Mom got the computer in 2004 if I remember right). I would think it could be dusty inside. TVs also act up when too dusty, so perhaps this is the CRT showing dusty signs.  Maybe I just need to disconnect, open the case, and blow it all out. I do have a backup monitor which has a bad wire (the red cuts out if the cable isn't properly placed) just in case. Maybe it's time to find a decently priced LCD monitor. I don't know.