First of all, you couldn't use a worse phone, I don't think you can issue AT commands to a Nokia 3310, its just M-BUS or F-BUS, so you need an F-BUS data cable, and a MAX232.
You will need to tie RTS and DTR lines down, wire DTR to the +V of the MAX232, and the RTS to V- of the MAX232. You will need to synchronise the bus to start talking, I think you have to send a character a number of times, can't remember exactly which character, I think its 100 times or something recommended.
Anyway, hitech c is probably the best as the lite version is free as part of MPLAB install.
To drive your lamp you can use a transistor and relay, if you are driving high wattage use a suitably rated panel mount relay (or I find automotive relays quite robust! Only rated to 12V though!!).
Be aware that you will have to "pack" and "unpack" any SMS messages using the 3310 and learn the F-BUS protocol.
Wilksey