depends how long it took you to draw...
this could be a rough year with the drought, so a 320 might be big this year? I'd ask the outfitter how he feels about this drought and antler growth?
If 320 beats your best elk that was 315 I think I'd want to hold out for more... but if you've never shot an elk or your best is 250 or something I'd probably take it.
If you want 350+ or nothing, tell your outfitter! but be prepared to be skunked...
you do hear stories of guys passing 320 day 1 then hoping for a 350, and end up skunked or shooting a 290 on the last day...