What is the typical time it takes to put an aircraft on a 135. Our aircraft is going on 135 .there are hurdles we have such as the FDR which was removed in the past I understand a new type FDR needs to be fitted.

Really depends on the FSDO CMT workload and how organized / ready you are. Most offices have a document / "job aid" for adding an aircraft to the certificate. Some things to consider are the readiness for conformity, training program, mel, checklist, contract check pilot approvals, and what opspecs you will need. Might be good to revisit the compliance statement as well.