Hi and welcome to RWG.
The 3714 is a stunning watch and I am glad you have found a project you wish to pursue. The rep modding game can take a long time but always be patient and work with the best guys around.
In EU, Hugo and Concepta do provide gen parts. I have worked with Concepta before and he is awesome. Unfortunately he is involved with so many projects that replying can be hard at times. However, the person he works with on the 3714s is a member called Texski. Texski is a guru in the 3714 and will do all the modding you need. His work is top notch but he is based in the U.S.A. But shouldn't be a problem.
I agree, you can start by getting the rep first. I would only use the dealers listed on this forum as this offers more protection. Try and source the rep with the "upgraded" movement as Texski has mentioned before that servicing this upgraded rep movement can be good. Ultimately however, and given the shaky history of this particular movement, the gen movement is a better choice.
Equally, the gen 3714s come with the double AR with a slight blue hue. Older versions didn't have AR but I would recommend double AR these days.
If Concepta is hard to get hold of, message Texski and let him know I sent you to him. Believe me, he looks after you from A to Z