There are so many good instructables on this subject, I will just make this part a quick one and let the pictures do most of the talking.
Removing the laser from the DVDR is not hard but most lens assemblies look different. Locate the diodes (there will be two, one IR and one red) and remove them from the assembly. There are some optics and two magnets that can be saved for future projects. Once you have removed the two diodes you must be careful. The two diodes are very small and fragile. Remove the small connecting PCB strips from the diodes and use two AAA batteries to check for the red diode.
Now that you have the bare diode it is time to mount the diode in the housing. Place the diode in the housing and use the back of the housing to press down the diode very carefully using a vice. When you get this far you are on the home stretch. Solder the wires to the positive and negative pins, screw in the lens and you are done.