I got the full spectrum conversion done from lifepixel, pretty pleased with their service
I like the IQ I get from the camera, pics are nice and crisp, noise seems a bit more, not sure if these are due to the conversion or just the output from a 600D in general as I bought it and directly sent it in for the conversion.
You need to custom WB everything, auto WB will not work, also I have read that the phase detect AF won't work in IR very well as the cameras are calibrated for visible light and IR focuses at different wave lengths, contract detect (the slow live view focus) works fine.
I use the MaxMax UV-IR cut for visible light and have Marumi 700nm, Tiffen red (around 600nm) and a cheapo 720nm for IR
I wouldn't touch the insides of the camera myself and what you have mentioned about the screws is very scary indeed.
Liepixel sells only the filters for DIY conversion but they cost 2/3 of the cost of the conversion, check them out if you are in need of the filter only.