You have to be of a legal age of 18 on the day you take your Basic Theory, Final Theory and TP tests.
Taking the Theory tests is easy, just buy the official guidebooks from Popular and read it up. If you can pass your N's, O's or A's, I don't see how you can fail these tests. Just need abit of memory power to remember all those signs thats all. No rocket science involved.
Though you can apply for your PDL once you pass your basic, I recommend you take your Final Theory Test first as the waiting time between tests is kinda a lovelovelovelovelove. Once you pass your Final Theory, you can book your TP and apply for the PDL together. So you don't really waste the 6 months validity of your PDL if you have to wait longer for your Final Theory or TP dates.
As for the TP, its all about your driving skills and confidence. If you can make your tester feel safe sitting in a car with you, rest assured you will have a new form of identification to show off with.