Satguru Rampal Ji Maharaj gives a very good clarification of the above questions in the 3 videos given below. Watch these in entirety to understand the full concept of doing true worship and gaining its benefits.
In short, Worship should be done with the aim of attaining salvation (Liberation / Moksh). Worldly benefits, prosperity and good health are by-products of true worship. However one needs to have firm faith in true worship of God Kabir given by Satguru Rampal Ji Maharaj. They need to abide by the rules of Bhakti and keep patience and then one definitely reaps the benefits of Naam.