This link might help you - take a digital photo first to give you confidence when reconnecting (not absolutely necessary) and you will need a soldering iron and the skills to use it. Capacitors are cheap and may be bought from any hobby electronics store such as Maplin. Be sure to put them in the right way round.
http://kaijaks.co.uk/blog/nick/2008/02/10/dodgy-old-boiler
However - I doubt that a hairdryer might make a failing capacitor begin to work. When my Potterton boiler responded to a gentle warming it was because the heat from the pilot flame was insufficient to trigger the next stage - due to a partially blocked pilot injector.
The heat from the hairdryer might also be helping to temporarily overcome a dry joint - tapping with a wooden spoon sometimes helps to diagnose poor soldered joints.
Good luck...
Peccavi, June 2011
