How to check rebuild indexes on database performance

Hello,

I'm going to rebuild indexes on my quite big database and then put it on a schedule.

I'd like to know if I could somehow verify the impact of index rebuild.

I expect that it should improve performance as well i.e. it should take less time to perform 'expensive' queries or etc.

My questions:

1. are there any 'standard' way of proving that index rebuild impacted database performance ?

2. could I run some 'expensive' i.e. slow query, then rebuild indexes , run the same query again and expect that it took less time than before?

Thanks

susja