I agree with [MENTION=98938]DeF[/MENTION]con1, don't make killing Strahd the goal. The point of Strahd is to be a recurring antagonist over the course of a campaign who takes time to turn into a proper villain. If the point is just to show up, bump a couple levels then kill a vampire, you don't need Strahd for that. IMO, it really kind of "cheapens" the Ravenloft theme.
If you want the Ravenloft experience though, maybe approach it from the aspect of Strahd as the quest giver. He needs something, and wants the entertainment of watching a group of powerful adventurers suffer in getting it for him (after all, that's why he brings people to Barovia, is as playthings). The Amber Temple and Strahd's Castle are both listed as Level 9 adventure sites, so focusing on those will take the least amount of re-work. Maybe it plays out something like:
- Use the classic Mists intro: after spending an unusually misty night in the woods, you wake up in a different forest, and the nearby road leads you into Barovia.
- Strahd meets you in his carriage. He welcomes you to his valley, and tells you he is looking for some help obtaining something from the Amber Temple. He's classically condescending - in return for helping him out, he offers you freedom from his prison, since he is the only one who can allow others to pass through the Mists, kthxbye.
- The players can enter Barovia at a place of your choice. They can have whatever encounters along the way to the Amber Temple that you want, e.g. experiencing the social politics of Vallaki, the hag coven at the windmill, assist the Martikovs at the Winery, etc. Maybe pick two or three key plot points which illustrate the dark nature of the valley, before they get to the Temple.
- Once there, the Temple is essentially a dungeon delve. There's some difficult fights there, and several opportunities for non-combat encounters (e.g. the lich is a lot more fun to talk to than to fight). Also, play up the encounters with the vestiges, and allow your players the opportunity to cut deals with them. The lingering effects could extend into your campaign beyond this side-trek.
- After the McGuffin is acquired, the players can head to Strahd's castle, and if you want, have a creepy-castle delve looking for him and experiencing the various bad things there. Once they find him, they can give him the item and he gives them their freedom.
- If you really want a vampire fight, place the final encounter in his tomb, and have Strahd decide to kill the PCs now that they've done what he wants; the Brides (vampire spawn) help make the encounter harder. If they can defeat him, they can escape the valley before the Mists close back in. In that case, make the McGuffin the Sunsword or Holy Symbol - Strahd wants it retrieved so he can keep it under lock and key, but in a fight, the PCs can use it against him, so the fetch quest feels a lot less random that way.
That would give you a good 2 levels, using milestones; 1 level after the Temple, another after defeating/escaping Strahd. Maybe a third depending on how many encounters they have before the Temple.
However you decide to play it out, be sure to play up the horror element - this isn't just another random monster filled valley, this is Ravenloft, the proverbial mother of all horror settings! Pull out all the stops, and have a ton of fun with it.
