no worries mate, you can always buy cheap spare Dreamcasts if you get issues, I think they go for about £15-£20 if your just getting the console with no games and cables... Shenmue and JSR to me are MUST HAVES, but Shenmue is only really a must have so that you can then play Shenmue 2 and understand it. To me Shenmue 2 is superior to number 1 in almost every way. I love Shenmue 1 but theres a lot to be said for pacing, it can get a little boring if you don't know where your going, though it is definitely an essential Dreamcast experience
enjoy and let us know what other games you end up getting