That would depend on your habits. Smoking, coffee, tea, and mustard are the most common sources for stains. Otherwise, Lasting Touch or at-home bleaching, and good oral hygiene will allow you to maintain a white smile without much effort.
I know if I want to bleach my teeth I would have to bleach before the crown is redone. My concern is whether or not it will be difficult to maintain the same shade of whiter teeth to be the same as my new crown in the future?
If you are planning on bleaching, bleach before having the crown redone. Porcelain will not change colors, and it will be near impossible to match the tooth if you bleach after. You can ask your dentist about a new product called Lasting Touch to help maintain your white teeth up to a year after bleaching.
I have a question about bleaching. Since I'm going to get #9 redone, should I bleach my other natural teeth? Is it hard to maintain? Will it be hard to rebleach my teeth in the future to match the new crown?
It's highly unlikely that either a prefabricated post or cast post and core will show through . PFM with porcelain margin or full ceramic crown will never show metal even after years of service.
The darkness seems to show 3-4mm above the gum as well. Could it be from the pre-fab post? Which is stronger a PFM with porcelain margin or all ceramic? I'm just afraid that a PFM with porcelain margin will show through in a few years as well.
Your descriptions suggest that metal margin of PFM may be displaying after years of service, which probably rsults from gum recession.Redo full ceramic crown or PFM with porcelain margin can definitely achieve your cosmetic demand. Removal of your current crown generally poses minimal risk. There is no need of touching cast post and core if it's still retentive.