More repair parts

So yesterday i broke my chain on my commuter (sram 951) after something like 3k miles.  So i steal a chain from my 29r same chain but more like 1500 miles.  On the way to work i notice it skips over the cassette so bad I had to walk a hill.  My cassette is a sram 970 or something like that with the same milage and totally covered in rust.  I give props to sram it still got me to work today (the largest 2 cogs hold the chain still).  I guess I'll steal the cassette from the 29r too and buy new parts for it.  So overall my review of Srams 9 speed is great this bike is only used in winter and some really muddy gravel riding and it still shifted perfectly up till the moment it broke.  I forgot to grease it last spring so it had rusted solid and i Rock 'n Roll lubed it back to life in hopes of no new parts this year but didnt make it.  So now to save up 50 bucks for some new parts on the nice bike.