Note that the correct term is accreditation, not certification; as it involves formal recognition of technical competence.
The period of implementation will depend on the size of the labororatory, the number of tests to be added to the Scope of work; as well as naturally, the available reources. Typically from start of project to application for accredition could be anything from 12 months onwards. Once you have applied, it may be up to 3 months before the accredition body perfom the assessment. You then would usually have 3 months to implement any corrective actions before being awarded accreditation. This means that for a small laborory, it may be a short as 12 months, but typically longer.
The costs will depend on the accreditation body. I suggest you contact them and request a quotation. In awarding accreditation, the accreditation body attests to your laboratory’s competence to provide consistently valid results through meet the requirements of 17025. An accreditation certificate, which details your scope of accreditation is then issued.