Well, updating a stadium to have a new video board or bowling in an endzone is NOTHING like creating a new stadium from scratch. Which reminds me, I had our lead stadium artist send me stadium estimates in case someone here asked... so this is a good enough time to post them so you can understand the amount of work they require.
Modeling is 160 hours
Texture (including UV Layout, locators and crowd strips) is 120 hours
Art Director Review and Changes- 16 hours
Lighting is 30 hours
Field Art (from scratch) is 8 hours
Bug Fixing (IF QA finds all the bugs in one pass) 4 hours