the side bolster is fading on the driverside seat of my TT? can it be re-dyed? Is this something I can do or do I need to go to a detailer?

yes, you probably can find a an aftermarket auto leather upholstery shop that can do this for you.
But you are most likely going to have to redo both seats in order to achieve a uniform appearance. There is also one big "but" to this process. You will most likely end up without the benefit of the proprietary top coatings that are applied to automotive leathers at the tanneries that produce them. Also, also automotive leathers are drum dyed for full penetration of the dye through the depth of the leather. The best you will likely end up with from the redo you seek is a topical application of new leather dye. It may look nice, but by nature of the beast it will never be as durable as leather that was colored through a full penetration drum dye process.

Has universal colors if you are going to redo the whole interior,
or you can cut a small 1x1inch square and send it to them and they can create an exact match.

it will save time, but you need to find an inconspicuios patch to cut out of.