Check out jackssmallengines.com for parts, as well as partstree.com. Their prices are usually within a few bucks of each other. And yes, if you go to sears for parts, dig deep.
As for mower quality, you somewhat get what you pay for. Cheap deals are usually that, cheap. Many times it is just plain luck, good or bad, when you get a good mower or a lemon. I have a 42" Craftsman rider, and it has cut my 3 acres for the last 10 years, and I plan to keep it another 10......... that would make me 73, ummmm.
I work on a lot of the Craftsman 42" series as well as other brands and the vast majority of the problems I find were either preventable or normal wear.
Any mower a person chooses will be no better in service as is the upkeep and planned maintenance that the unit gets.