Silver metalic is very hard to match as the finish appearance depends on application air pressure etc. Tell the body shop to paint the whole car but include the additional in the insurance cost or most of it.

Usually not a lot more work than painting basically one side. On top of that your old silver might be faded. I know a color match spectograph can match the fading pretty well but it cannot help on how the present silver was originally sprayed.

Depending on your insurance company they may even baulk at painting any more than the fender. Hopefully your company is a little more generous. I could as easily develop a rant about my love for insurance companies.