For selling your spare bits I'm a fan of free internet advertising, here, CL other sites whatever, free exposure doesn't cost you anything
On the shows, I assume you are referring to the west coast nationals on Orange CA? I actually attended that one in 2012. "Z Dayz" at tail of the dragon is coming up in mid May. Branson Z Fest is at the end of May. Midwest Z heritage show travels and is in chicago area this year mid June. The ZCCA National convention is in Memphis this year, mid July (I'm gonna try and make this one). In the fall Z1 has what they call "Z Nationals" it's really centered on Z32 and newer models, they accept older cars but don't expect many, or much attention. Normally the MTZCCA hosts Z Attack in april but it doesn't appear to be happening this year? You might also find some local shows. The ohio ZCCA chapter has had some issues in years past but used to put on some good sized local events, so did INDY. My local Bluegrass z car club hasn't hosted a show in several years now.