The order you should be buying these albums in, if you liked the songs off of Good News, is this.
Get Good News First. Yeah, it's their sellout album, and it's their poppiest album, but a couple of the songs will get you ready for some of the rougher stuff, and it'll be an easy place for you to start.
Then get Moon and Antarctica. This is a really great record, without a single bad song on it. It's still a lot easier to listen to then their earliest stuff, but again, you can hear the more experimental sounds creeping in around the edges on some of the better tracks.
Then you want to get Building Nothing out of Something. It's a combination of all but 2 tracks of the Interstate 8 EP, and a lot of other singles and B-sides they put out early in their career. It has a ton of really amazing songs on it, some of which rank among the best the band has ever done, but it's still less difficult to listen to than some of their other stuff.
By this point you're ready for Lonesome Crowded West. Flat Out, this is the best Modest Mouse album. There is literally not a bad song on here, and it has my two favourite songs by the band, ever. Buy it, listen to it, love it.
After this, you can get This is a Long Drive for Someone with Nothing to Think About if you want to keep yourself off the edge, you can get Fruit that Ate Itself if you want to run screaming over the edge and listen to some of the most intense music they ever made, or you can get Sad Sappy Sucker, which is a reissue of their original EP's, plus what was supposed to be their first full length, and which I do not have, which I am incredibly unhappy about.
Just my 2 cents.