Gauge decals.Should i remove the faces?

[COKE]

I,m going to install the face decals on my gauges,but  i don,t know if it will be better to remove the face from the gauge for the job .
Not very happy with the idea.
Also would like to know if it will be necessary to paint the small gauges faces before to install the decal.
The gauges have not rust.

Thanks in advance.

[dkn1997]

you just have to take the whole entire gauge out of the cluster, no need to disassemble it further.  just use a cut straw to cover the needle and be very careful when doing that. easy to wreck the inner workings for the gauge. 

I recommend painting the faces black, clean slate and all.  plus you will find that even they don't appear to be rusted, they are once you get a good close look after removing them.