If you have a good knowledge of at least one other language, a legal background will mean you are well placed to become a legal translator. Although further qualifications are not essential, you will obviously be taken more seriously if you have one. A post-graduate diploma or master's in translation is a common route and at least one university is now offering an MA in legal translation. These courses are often available on a part-time or other flexible basis which could be combined with continuing in your existing job. Another option is to try to obtain the well-respected professional qualification awarded by the Chartered Institute of Linguists, known as the Diploma in Translation. You can study and enter for this independently or there are a variety of preparatory courses, often run in the evenings or by distance learning.
Although in-house translating jobs do exist, they tend to be few and far between, unless you are tempted by the international organisations route. Many of these employ legal translators. The EU, for example, employs 'lawyer-linguists', who are required to have a legal qualification. To obtain a permanent job as a lawyer-linguist you will need to be selected through an open competition procedure, which is a long drawn-out affair to say the least. Temporary contracts are, however, rather easier to come by and may be a good starting point, although the job will not be made permanent without your going through the open competition procedure.
Many translators work on a freelance basis. There is no denying that starting out on your own can be hard but you may be able to use your existing contacts in the legal world and having a legal background gives you an immediate advantage over generalist translators.
Conference interpreting is a highly specialised career for which post-graduate training is virtually essential. A less pressurised alternative is interpreting in courts, police stations, hospitals etc. Here again the Institute of Linguists' Diploma in Public Service Interpreting is an excellent basic qualification which is taught in colleges around the country on a part-time basis. One of the specialisations offered is law.