How to change ground/sky on photos

[strange flicker]

Hey, so I've got a client that wants me to change the skies/ground on the photos I take of their cars. I feel like this is a great opportunity for me to learn how to do that and some other things. How would I go about replacing the sky and the ground realistically? I've tried to delete the background and then use the sky replace tool but nothing really worked up to my expectations.

Cheers

[jagged lance]

I assume you've tried the straight up 'replace sky' tool? - Why did it not work? What happened?

[strange flicker]

The thing is, it works. But it's not realistic enough.

Here let me show send a few photos

Before :

After :

[jagged lance]

Looks pretty decent to be fair

[strange flicker]

Well maybe I feel like it doesn't because it's missing some background elements then