I’m sure Drakan will correct me if I’m wrong, but you should sell as a resident to pay less CGT, 15% (assuming you have held for longer than 1 year) compared to 35% as a non-resident.
I expect that the resguardo you are given when applying for residency renewal will be fine. Anyway, if you apply for renewal now you’ll have your card in a couple of weeks. And anyway, your card is not as important as your fiscal status, which is based on the number of days you spend in Spain during a calendar year. More than 183 days here, then you’re a resident for tax purposes, like it or not.