"A period of fourteen nights; two weeks" (OED).

“A call should be returned with a call, a card with a card, within one week, or at the most, ten days.” (Hoppe "Calling Cards and the Etiquette of Paying Calls")

Ten thousand pounds is somewhere around 1,090,000 GBP adjusted for inflation from 1800. However, inflation rates vary; so this number is approximate ("Historical UK Inflation Rates Calculator").

For context: Miss Bingley, and Mrs. Hurst have twenty thousand pounds (ch. 4). Miss Darcy is worth thirty thousand (ch. 35). The Bennet sisters are splitting their mother's fortune of five thousand pounds (ch. 50).

A fashionable street in the Mayfair neighborhood of London's West End--where 'society'dwelt. The most expensive, and desirable street is Park Street, and Grosvenor Street intersects it. (Pool What Austen Ate... 28, 51).

Hunsford: a fictional location in Kent; where Mr. Collins is the rector. ("Important Places in Pride and Prejudice and Jane Austen's Life")

Kent: county in South/East England along the coast, opposite of Dunkirk, London is slightly Northwest. (Google Maps)

Hertfordshire: county in southern England, just north of London. (Google Maps)

"'In spirits': in a cheerful mood; animated, elated, happy. 'out of spirits': low-spirited" (OED).