I have the dealer service my car for most matters in part because I don't have space to work on mine (shared condo garage). However, another big factor is that I want to have Aston service records for resale purposes. I think this is more important for marques like Aston than for others.

 

I paid $1600 for the lights at Los Gatos AM; install was another $360.

Also, if you do it yourself, be sure and pick up some replacement seals which cannot be reused (6 total at a cost of $3 each). I recently had my car wrapped in a clear bra and the tail lamps were removed without replacing the seals. There was subsequently some leaking and the AM tech explained to me that the seals are a one-time use thing because of the way they mold to the area. No more leaks after the seals were replaced. Thankfully the place that did my clear bra picked up the tab at the AM dealer.

 

I got my taillights from RSC. The new seals were included in the box the lights shipped in.