If this is your first time in India then I would really recommend getting a good nights sleep in a nice hotel on your first night. Most of the low budget hotels can bring quite a culture shock. If you land at 11pm then I am preety sure you won't get to your hotel by 1am. I landed in DEL a few weeks back and took me 1 hr to clear immigration and another 30 mins to get out.
I am guessing that you haven't booked your train yet from Delhi. You have two choices - The best is the "Shatabdi" leaves Delhi (C.P) at 6.30am (ish) and gets you to Ludhiana by 12ish. Try and get your self a Executive class ticket for this as its much-much better then normal a/c chair class. The fare is twice as much as compared to normal chair at Rs500 o/w. Only stops once on the way and is quite fast.
The second choice is the Shane Punjab. This is all one class train and leaves 8ish from Delhi. Not recommened as its stops at every major station and is quite slow.
I would recommend that you stay somewhere near Connought Place! That way you can make it for your early train! Try booking via Google websites.
I really would not recommend flying in, sleeping at 1am and then waking up at 5am to go for your train to Ludhiana. Is it not possible to break your journey for a day?
Another thing you could do is get a good nights sleep and then get the IA flight (40mins on a Airbus A320) to Chandigrah at 1pm the next day ($40...Rs1,750 o/w) and then get a Taxi to Ludhiana or get someone to pick you up. Its only an hour from Chandigarh. Will be a lot better then spending 5 hrs in the train. Although the Shatabdi is quite comfortable. There is also a evening Shatabdi that leaves at 4ish.
I would really reccommend that you book your Train in advance (via Indian railways website) as getting a ticket is close to impossible within a week of travel! (seriously) Also book your hotel in advance, the hotels are extremely busy in Delhi and the last thing you want to do is go from Hotel to hotel in the night. Taxi's are perfectly safe though.
I am currently working in and around Ludhiana. Feel free to PM me if you need any more help or advice.