I have a 9 week old rottweiler and it took him 2 days to learn to do his business in the backyard, not on the deck/in the house, so we're happy about that and he does it all over the grass.

I'll be putting new grass in (old one is terrible) so then I'd like to get him to go at the end of the yard instead of all over the place.

Question is will it be hard to get him to do that or should I start now by taking him always to the end of the yard?

At night he already goes on his own, I just open the door and let him out, he does everything and comes back in 5 minutes.

It might be difficult, since the new grass won't have his smell and therefore won't be "his" territory. He will try to mark it instinctively.

Definitely get him used to going to the "latrine" area before the new grass comes in.

It might be next spring before new grass is there so should I be taking him to the designated area now or even after a few months it would be easy to get him to go there and now all over the place?

It's just that now since he goes 3-4 times at night (when it's dark outside) it's easier to let him go anywhere than to always take him all the way down to the end of the yard (about 200 feet)

I know this might not be what you want but I will suggest it anyway...

Try buying some plastic garden edging and making a 'box' where he is supposed to go to the toilet...
The garden edging is only about 20cm high and easy to walk over but it will teach him that there is a certain boundary where he needs to go...

While he is only a pup you could leave a little walkway for him to go in there until he is big enough to step over it.

I know this might not be what you want but I will suggest it anyway...

Try buying some plastic garden edging and making a 'box' where he is supposed to go to the toilet...
The garden edging is only about 20cm high and easy to walk over but it will teach him that there is a certain boundary where he needs to go...

While he is only a pup you could leave a little walkway for him to go in there until he is big enough to step over it.

That sounds good, I'll give it a try for sure. At first I though he'll want to go in an area where there's no grass so he can dig but he goes on grass no problem so I'll just designate an area and keep taking him there.

Very Good idea, Shaz.

My next pup I think I'll try that one, too.

Thanks guys, a friend of mine does it and it works for her...
Once a day she gives the 'box' a light hose down to wash away the wee, best part is, her grass is still green!

Had the spread the rep shaz, but great idea!:D