Doggy Door
 

I would like any information and/or advice you can share on installing a doggy door thru the wall of the house (vinyl siding) into the screened-in lanai. Specifically, how hard is it to do? When you go to sell the home, how hard is it to restore to original condition? What other options might be better? And if you've done it and used a handyman, who did the work and were you satisfied? Thank you in advance.

My husband installed our doggie door. We love it.

I had a doggie door that you put into the slider. It installed very easily and you could remove it also very easily.

Check-out these pet doors for with your sliding doors on Lowes:

Shop pet door at Lowes.com: Search Results!

I installed one for the cats. They love it and I can still have the sliders locked.

Consider adding it to the bottom of a screen door if you have one, much easier and should not be a problem if you sell.
Another option would be to purchase one of those slider screens that you can put in your lanai window. Put the doggie/kitty door one one side can insulate the other with foam. At night or when you are away, it just slips out and you close the window.

I don't work for this company but I sing it's praises:

POWER PET DOORS ON SALE HERE! Dog Doors Cat Doors, Pet Operated

They do all types of pet doors, through screens, wood doors, siding. We have their electronic model and it simplifies our life and keeps the heat and cold in. Our dogs figured it out in about 2 tries. Customer service is unbeatable. They even replaced a collar that another dog chewed up at doggy day care--no charge. They recently replaced our entire door for only the cost of shipping. It had been installed 3 years ago. Very friendly on the phone and they don't mind questions. Shipping is reasonable. Love them!