Be careful with sodium hydroxide - it has a habit of turning you into a sloppy mixture of sugars, amines, monosodium amino acid salts, glycerine and soap. Not nice.
Sodium hydroxide should only attack polymers that are susceptible to nucleophiles and bases so most plastics used in the old yellowing cases should be fine. Certian materials like polyurethanes and so on might be allergic to it.
As for that oven cleaner aroma; you can't place sodium hydroxide by smell though. And if you could, it would dissolve your nasal tissues rather badly.
