i agree with astrobaby, the best place to take it would be an auto repair place, they have the best tools for getting small dents that have not creased the metal, All you can do is ask, they will be able to point you in the right direction!
Many thanks for the help from all the members. Appreciate it. I am going to take advce & go see a specialist panel beater or silver smith to see if he can do a job on the cap. When I get it done I will post pictures on the web for the finished Lunar lamp ! I hope :-)
no-one in their right mind would offer a half refund for a lunar just on the basis of the cap being dented, its relatively simple to sort out and the lamp is worth too much.
if someone wanted a refund bad enough, the seller could have it back and give a full refund, or maybe knock a bit off for the money you'd have to spend to fix the cap, but i doubt it would be alot.