Morning Reg - some good advice above.
I used to do a lot of long distance touring - I always found w/p trousers a waste of time - just get wet legs, and, if you are wearing lycra this dries incredibly quickly once the rain stops.
Another vote for chamois cream and good quality shorts (which are not cheap) - I used Assos shorts and cream, but they saw me through several 1000+ mile tours, and riding 8,000+ miles per annum with only one saddle sore. Shorts for cycling are like boots/shoes for walking - the most important bit.
Gloves - I used Altura or Gore but avoided gel gloves as, in my experience, these tended to degrade more quickly. I never bothered with w/p gloves - none work in my experience. And go for a thicker bar tape for comfort.
I never bothered with a w/p helmet cover - I wear a cycling cap under the helmet - as I am follicly challenged I used to get a helmet shaped sun tan on my head!
If you are doing a multi-day trip you will need to think about kit to carry too! I can let you know what I sued to take and there's a great blog here
http://ultralightcycling.blogspot.com/He's a complete madman but there's plenty of food for thought - he was my inspiration in getting kit to a minimum, though I was never as dedicated as him.
Enjoy
Paul