It might cost a LOT less to buy another case. By the time your case is totally taken apart, polished, detailed and plated, you might be in Deep $$ Water.
Example:
The last YGP over steel Prez (with Asian 21 jewel mvt) I bought was $99 iirc. Do not know how good the plating is because I never wore it.
Also...if you get another case, be sure it has the 'half hooded' lugs if yours does, or the bracelet will not fit.
Btw...I kept an aftmkt 18K Prez case that I got in February 2001 but the dial seat is about 1.5mm too big to accept oem dials. It weighs a hair over 30 grams so I've been thinking about scrapping it...30 grams 18K gold is over $1600 today and a jeweler friend will pay 85% for it = about $1350.
Why in the world they made the dial opening too big I'll never know.