Lunch for an adult (as of last year) was conveniently the same price as a one day one park ticket- but the ticket that came with it is a park hopper. I want to say the child's lunch was $37.50.
Go. If you can possibly swing the money, go. It is absolutely wonderful. Do not cave into the temptation to act like you do it all the time- tell them it is your first visit- they have always pulled out all the stops when we have had (or been) first timers with a tour and some history and little freebies- pens, tiny notepads, extra mints etc. Also note that this is your only opportunity to buy the keepsakes sold there, so budget for the ears or pin. IIRC ears were $15, Christmas ornaments were $33 and the two pins I have varied widely- one was $10, one was $33.