Trekking from Manali, India

Hey...
So I'm gonna be in Manali around June 9 and want to do around a three day trek, probably Manali to Lahaul. I have no gear and am a complete novice. So I have a couple of questions, and any help would be much appreciated:

1) Is this an advisable trek for novice (I'm a 29 yr old male and in good shape)?

2) Can you recommend a trekking company that will organize excursion? What can they provide?

3) Is a jacket necessary during this time, or will 3 layers consisting of a thin cotton undershirt, light polyester thermal long sleeve shirt, and heavy cotton longsleeve shirt due? (I guess I could throw in another cotton t-shirt also, if necessary

Thanks so much!!!