Extra info on this series for the new GTE cars...NOTE that though not mentioned in the release notes THERE ARE SOME GOLD REWARDS as well as M$ rewards 
There are 42 events (36 Trophy + 6 TT) with only one of the cars necessary to complete the series, and progress progress through is wholly reliant on Driver Level and the small amount of PR that adds to base stats.

The rewards are split:
25% - M$8000 + 8GC.       Driver Level 2 needed
50% - M$13000 + 13GC.   Driver Level 4 needed
75% - M$18000 + 18GC.    Driver Level 5 needed
100% - M$27000 + 27GC.    Driver Level 7 needed

PR Gates/Walls occur at these Tiers:
2.3 - PR63.8
4.3 - PR64.0
5.3 - PR64.1.         (6-lap Monza 1016XP)
7.3 - PR64.2.         (6-lap Nürburgring 900XP)
8.3 - PR64.4.         (7-lap Daytona Road 1191XP)
10.3 - PR64.6.       (7-lap Mt. Panorama 1262XP)
11.3 - PR64.8.       (7-lap Silverstone GP 1198XP)
13.3 - PR64.9.       (10-lap Indianapolis Road 1175XP)
14.3 - PR65.0.       (7-lap Spa 1437XP)
16.3 - PR65.2        (8-lap COTA 1273XP)
17.3 - PR65.4.       (5-lap Le Mans 1979XP)

At some points the car you chose will have an effect because of their base PR.  XP farming possibilities *EDIT* now above including Rob NL's info  *EDIT* plus more from Marcel's - see his post #6 below for XP/Minute calculations

*EDIT*

Done, and won't be going there again any time soon - total grindfest