Hi WelderMan

I only have a 2010 edition handy now of D17 but will give you a response anyhow.

5.2.2.1 is the clause that provides your guidance here.

Welder Performance Qualification is governed in clause 5 for all aspects, whether production or repair, whether Class A, B, or C welds.

The repair WPS (made in accordance with Clause 8) will contain the essential variables listed in 5.2.2.1 and this will dictate the performance qualification testing for the welder making the repair.

To answer your question:

My question is: Does a welder for the repair of existing structure welds need to meet the requirements of Clause 5?
Yes

Does the welder need a test record for all the correlation factors (Base metal composition group, base metal thickness, etc.) for the repair of existing structures? or is this only for production welds.
Yes..  All welds

A welder must pass performance qualification testing of a Class 1 weld with a written WPS.   This does not change one bit if the work to be performed is a Class A, B, C...  or if the weld is a repair defined in Clause 8 as Critical, Semi-Critical or Noncritical.  

The WPS's may vary from production to repair.  This will be driven by the Engineering Authority and their judgment.

Clause 8 says nothing about the performance.
8.4.1 Welders and Welding Operators shall be qualified per Clause 5 to perform welding using the equipment specified by the welding procedure.