I just completed replacement of the timing chain, etc on my 2011 LR4, 115K miles. I did the work myself and truck runs and sounds like new. With that said, there are a few things that I can pass along regarding the injectors.
There are two methods for replacing the faulty tensioners and guides 1) replacing only the tensioners and guides - there is a procedure on Topix that outlines how to do it, but it can be tricky to keep the engine from jumping timing, however the valve covers / injectors are not removed. 2) full out replacing the the timing chain, crankshaft sprocket, tensioners, guides, gaskets, etc, The later is a better longterm fix but more expensive and yes requires addressing the injectors. I did option 2 as my timing chain was indeed a stretched. While the injectors are a solid piece of kit, they can take a beating upon removal using the Land Rover Injector tool. In my case, the #8 injector was very difficult to remove, this is the one that failed. Got the replacement from Atlantic British-worked beautifully. Theoretically the injectors will last many, many miles...however when removing them, one must be very careful to keep things clean, in order for reassembly, and take into consideration potential damage from removal. If you're having LR do the work, they will replace them with new- it's the easiest thing to do. If you choose not to replace the injector, you still must replace the seals (seal kit is about $21 per injector and bosch tools another $50-60) so you're in for $200+ no matter what- for a couple hundred bucks more you can put in new injectors.
If I had to do it over again, I would go this route. As an aside, Land Rover Brentwood TN is where I get some of my parts via online. They're cheaper on somethings vs AB- so you may want to check them out.