Hello all,
Please correct this text.

"Would you like to come in please?"
"Yes, thank you. I am very pleased to meet you and your husband. I am on patrol every evening. In case of need you can/may/ might(which of them should be used here) address me anytime."
"I think I will avail myself of your help/offer reight now. I have to go to a/the drugstore but our car is in the workshop."
"I will/would be glad to give you a lift ma`am."
Thank you. I will tell my husband (can I use "warn", does it require "about") and come down in a minute."
"We can go now."

Should I use "about" with tell. I know that when I mention something for the first time I should use an indefinite article. But when there is a concrete "drugstore" or "workshop" which of them should I use?
And my last question. When I want to say ' which of them should be used here" is it necessary to add "in this sentence".
Thank you very much.