First thing to do is honestly ask yourself can I do this to a standard I will be happy with or should I get a pro to do it. Silvers can be difficult to spray if you have no experience as they are prone to mottling on large surfaces. If you do decide to give it a go buy a bonnet from the wreckers and have a practice first.
There a 2 options what paint to use, acrylic or 2 pac. 2 pac is what your car is painted in now and is far superior to acrylic but it does have some serious health issues and shouldn't be sprayed at home so try and hire a booth if possible or if you do do it at home make sure you have a good mask and and a way to vent the fumes. Acrylic is a lot less harmful but will require sanding and buffing to bring up a good gloss finish and isn't as durable as 2 pac.
Nozzle size usually 1.3 or 1.4mm for 2 pac base and clear and 1.8 to 2mm for primer, Acrylic 1.8 to 2mm for everything but this varies a little so ask your paint suppliers they will have a tech sheet on their brand of paint that will give full recommendations on tip size, mixing ratios drying times etc.
Nitrate silver has a few variants as well so you may need to blend into your front guards to achieve a good colour match.