Don't overthink it, it's about you getting work done.
I have yet to find a translator software that correctly translates expressions like "overthink" in a way that's actually used in the target language. At least that's the case with Portuguese and Spanish (both of which I'm fluent in).
In this case I'd translate the whole sentence in a different way, rather than choose word for "overthink". For example,
Меньше думай, больше делай --> Think less, do more
Глаза боятся, а руки делают --> The eyes fear but the hands work
Considering "to overthink", I doubt if there is a good bookish word but commonly people say "зацикливаться", i.e. "don't overthink it" --> "не зацикливайся на этом".
There is also a couple of "slanguish / teenager" variants: "не загоняйся" or "не парься" (the latter stands for both "don't think / don't worry").
UPD. OK, for this case "мудрить" seems to fit nice:
Ты не мудри, просто сделай свою работу
Just my five cents, a bit closer to the original phrase:
Не думай больше, чем надо. Суть в том, чтобы ты сделал работу.
with an emphasis on a word "сделал" (Do not think more than necessary. The point is that you get the work done).
Even closer, a bit clumsy, but acceptable (I could say so, but primitive minds could get stuck in an attempt to extract the matter from the sentence):
Не думай больше, чем надо. Вся суть в выполнении работы тобою.
(Do not think more than necessary. The point is in accomplishing of the work by you)
I find the last Matt's variant (не мудри) is the best one.
Basically чересчур замороченный is exactly too overthinked- it's just that unlike overthinked, замороченный is acceptable only in colloquial speech.
So, in some cases it's acceptable to use заморачиваться or загоняться (more slang), so one can say something like:
Не заморачивайся слишком уж, тут главное чтобы работа была сделана.
or
Не загоняйся, главное - сделать работу.
