Can I order on line and pick up at my local wal_mart store?

Of course

Yes

Yes , I did that with my tires and they put them on free of charge because I bought them through Wal-Mart. The tire were also cheaper on line then in the store

Yes and sometimes you get a discount for ordering it on the website and then can in most cases go pick it up same day with a nice discounted price you'd if otherwise not gotten it