Do I Need New Optical Drive in My Mac G4?

In 2006 I purchased a used Mac G4, mirror front with dual processors (not Intel). For OS I have the Leopard 10.4.
Everything works great, I appreciate the machine.
For years I've viewed (rented) DVD movies on the Mac. Mostly it opens the DVD player without problems. Lately, it does not respond to DVDs in the drawer. Occasionally, when I insert a movie DVD, no icon appears on the desktop, and the drawer opens. Sometimes a prompt appears "Cannot find supportive disk".
Oddly enough, I will insert a movie DVD I watched the previous evening, but now it refuses to open the DVD player and the drawer opens. So it can't be defective DVD disks. This leads me to believe the optical drive may be faulty.
I have no problems playing (or burning) music CDs on the same drive.
Will I need to replace the optical drive?

To answer your last question first, probably 'yes'. [Incidentally, don't try to compare the playing of dvds with cds, there's quite a difference.]

Quality new optical drives are relatively cheap (I'd recommend Pioneer brand), and your G4 will accommodate a dual-layer dvd unit. Drives are easy to install, especially inside a G4 tower machine.

Your present optical drive may just need a clean of the laser lens, which can be done with a cleaning disk (some question about its effectiveness), or with a cotton swab and cleaning (isopropyl) alcohol. Getting at the lens is the hardest part.

Btw, Leopard OS is 10.5 (10.4 is Tiger), not that the OS should affect the operation of an optical drive.