1995 GMC Jimmy Setting Engine Timing

GMC Jimmy 1995, CPI CMFI Fuel Injection, 4.3L V6 Vortek. The VIN # 1GKDT13W6S2547512.

I am trying to adjust the timing on this vehicle.
With Timing Light, while engine is at 800 rpm idle
the Timing is reading ~ 10 - 15 % Advanced.
Two problems here:
(1) The Haynes Repair Manual which I am using, reads that you can adjust (rotate) the Distributor once you have loosened the Hold-Down Bolt. The manual reads : "( Ignition Timing Check and adjustment ( 1994 and 1995 VIN W and Z V6 only)." On my vehicle their is a hard plastic distributor Position Lock which is not letting me rotate the Distributor.
How should I proceed?
(2) Prior to Timing meassurement. The manual states that you must bypass the timing system. Locate the single tan with black striped wire that is connected to the distributor.
My vehicle has two separate wire bundle connections.
It does not have a single tan wire.
I know one is for the Camshaft sensor, however, I do not know what the other small 2-4 wire bundle connection is for. The second on is not a single wire per manual; it is 2-4 wires?
For a Engine of this age is 10 -15 % Advanced a reasonable timing setting?

Can you correct / help with this Timing Adjustment process?
Thank You for the help.