Here's my super quick guide to losing Vampirism:
You easily find 5 Grand Soul Gems at each of the Mages' Guilds. For example, there's one in Anvil, Bruma, Cherodyl, (lmao edit: I meant Cheydinhal) Chorrol, Bravil, etc... Either buy them fairly from the person who sells them, or pickpocket them but make sure you still have it when you walk out. I had some weird bug happen to me that caused me to not have it once I left the place.
So that will take you about 20 minutes if you find each guild house and the person to barter it from.
Then you collect the ingredients. The 2 bloodgrass you should already have; just find an entrance to Oblivion. You don't even have to go in, there's usually a couple shoots of bloodgrass sticking out just around the portal.
The nightshade took me about 20 minutes to find... Just run through the area between Skingrad and Bravil and you will eventually find some of them spread far apart. They look like a weeble wobble with purple leaves. Very droopy plant. You need 5 of those.
The 6 garlics are very easy, just go to Weynon Priory. In Jaffre's area, there are 2 baskets that each hold 3 garlics. In fact, one of them is on his desk. The other is on the shelf near the entrance to his area.
Stab an Argonian with your Enchanted Blade... but not Amusei. I made that mistake and had to pay a fine to the Thieves Guild. :-)
Follow the quest marker to find the vampire to get his dust. It's a pretty straight-forward dungeon run and the dude at the end fist-fights you and goes down pretty quick. Not a big deal.
All in all I would say you will probably spend a few hours trying to get this cure, and then you have to go give it to that dude in Skingrad for his dead wife. Ahhh! But don't worry, you still have it in your inventory once you give it away, or at least I hope you do -- I did.
And you get 2500 gold for completing the quest.
BY THE WAY, If you can't go out during the day because it hurts, you need to FEED -- Feeding on sleeping bums or whatever will keep the sun from hurting you during the day, but you have to make sure you feed every night. It also makes you look more human when you feed, and people will talk to you. If you don't feed, you'll look like a monster and people will yell at you. :-)