Hey i give a clue.. u give a try urself.
consider
ptr [ current node after which u want to insert or delete]
ptrnew [ is the node to be inserted/deleted]
Insertion:
ptrnew->next = ptr->next;
ptr->next = &ptrnew;
deletion:
ptr->next = ptrnew->next;
free(ptrnew);
try with this clue.., :D