Can you tell me if there are psychological services to deal with leg amputation?

Yes there are. Your surgeon performing your amputation should be able to put you in touch with your local services. The amputee coalition is an excellent resource. Here is the link: http://www.Amputee-coalition.Org/.
Ask rehab. The best thing for that is talking to your rehabilitation physician and to previous patients with amputations about there experience, usually rehab facility can facilitate that through the amputation clinic.