For re-issue of an expired JAR-FCL licence, you will need to hold a valid Class 1 or Class 2 medical and hold (or have held in the preceding 5 years) a valid class or type rating.
No you wont need to retake the exams, just training as required and a skill test.
The 'skill test' that is referred to above is the class rating skill test, not the PPL skill test.
How much training is sufficient you say? That's up to the CFI of the school you attend
There is no mandatory training requirement - refresher training is at your own discretion and not that of the school, although you may wish to take their advice. You are also at liberty to choose the FE/CRE to conduct the skill test
Provided your license is less that 10 years expired you should not have to do any theoretical exams
There is no requirement to re-take the PPL theoretical knowledge examinations no matter how long the licence has been expired.