(defun electric-+-suppress (n)
  (interactive "p")
  (cond
    ((< 1 n)
     (self-insert-command n))
    ((looking-back "#\\+" (- (point) 2))
     (delete-backward-char 1)
     (insert "-(and)"))
    ((self-insert-command n))))

(add-hook 'lisp-mode (lambda () (local-set-key (kbd "+") 'electric-+-suppress)))