One Dark Front Tooth - Options?

It sounds as if you are on the right path, treating infection and pain.  Once complete, it is likely this tooth will need a full coverage crown if not a veneer.  The challenge for the dentist will be to match this tooth to the others, not just in color but in shape, contour and texture.

A consideration here would be to KöR whiten all of your teeth prior making the crown or veneer.  This would make it easier to match color AND brighten your smile.  Your dentist will likely need to use a material that is opaque enough to block the color of the darker tooth and still look natural.

Doing this well takes a talented and experienced cosmetic dentist, as not all dental offices are equipped to deliver aesthetic results to such challenges.

A veneers is a thin piece of porcelain that is translucent, so light passes through it. It is not a good option for masking a dark tooth.

You could try internally bleaching the tooth after the root canal is completed. There is a small risk of root resorption with this procedure.

The other option is to place a crown over the tooth to block out the dark color. 

My material of preference is a zirconia/porcelain crown.

Matching ONE front tooth is about the most difficult challenge a dentist faces, even one with much cosmetic experience.  If it's also dark from trauma, it's that much harder!  I would usually recommend bleaching everything first, seeing how light you can get that tooth, and then doing an all porcelain veneer or crown, depending on the amount of tooth structure remaining.  I usually try to avoid placing a post if there is sufficient tooth structure left, as they tend to weaken the teeth.  This link shows a patient post-trauma where one porcelain veneer was done on the dark tooth after bleaching.