You should have a 1-sheet… think a basic Dj resume, but not so heavy on the text. Show pics from other parties you’ve done and a short paragraph on what you play, where you’re from and what sets you apart form the other Djs in town. Do the math before giving the Manager a quote (quotation), how much does it cost you to get there? How many hours will you be playing each night? How many nights a week? What is the average for a club dj in your town? How much do you want to make a month from playing regularly in this hotel?
Also include in the email a link to your website/Facebook page and press kit (pics, logo, event flyers that feature you on the bill, general price list etc) as well as a mix that represents your style and fits the vibe you want to bing to the hotel club if you intend to deviate from the current music policy. If you’re not planning on changing the general styles played at the club then make a mix that fits the current music policy and is not exactly what the current/previous dj plays.
good luck!