My landlord is refusing to fix heat, hasn't worked for 2 years so I withheld rent this month and he gave me 30 day notice to move out. I have documentation from heating Co. dated two years back saying heater needs repair. I am going to move out but can I get a portion of my rent back for not having heat the previous years. If so what do I need to do I live in NJ thanks a lot.

No, you can not legally just not pay rent, you could have sued for it to be done and set up a special escrow accouint and put the rent in that account so that when it was fixed they would get the rent. ( if the court decided it should be done) Can not believe you lived there for 2 years with NO heat, But all you will get by not paying your rent is evicted.
If you can prove that the home is not livable, by having building inspector check out the building, you may have a case against them for varoius costs.