read a guidebook. the rajdhani express is your train from calcutta to delhi.
since you are flying from the US, i'd be interested in knowing the price quote of your ticket. then one could debate whether it is really a good deal or not...
happy travelling
pallav
IMNOTANACCIDENT - i agree with pgupta: READ A GUIDEBOOK, THIS IS BASIC STUFF!
DOC MIKE - i've spent 2 years in India over the past 10 years and never bothered with malaria prophylaxis (although i would say on paper one really should). Some years i would never get a bite, despite friends around me being bitten; other years i got bit. Anti-malarials do not protect against all those other mosquito-borne diseases. The best advice is don't get bitten - ie. right clothes, nets, sprays.
In 2003 the trains into Udaipur were narrow gauge - buses actually make sense there. If you're going straight from Mumbai to Udaipur i would consider one of the train options to Abu Road or Jaipur, then a bus from there.
One tip I'd give about long distance train travel in India. Always book it yourself at the railway. I was stuck in Goa for more days than I cared to be waiting for a travel agent to book my ticket. Otherwise it's great fun. I took nine train trips in the two months I was in India and loved it. Take advantage of the coffee/chai cups offered for 5rupee. Sweet, but part of the experience.
Oh and as for the antimalarials. I personally am not a fan. Can lull you into a false sense of security which is when you'll come down with dengue or chikengurnia (sp?) particularly prevalent in the south.
Malaria, in all honesty, is the least of your worries when it comes to mosquito borne diseases.
Don't leave home without the Super strength aerogard ... and use it whenever your out, and request mosquito nets and/or plug in repellent/zapper thingies in your guest house or buy your own.