RonMed

Hi, Intermittent wipe function does not work. Garage say this is because the rain sensor isn't working and so the system doesn't think it's worth wiping the windscreen. Sounds reasonable. Price to fix = £345. Sounds unreasonable since the part would seem to cost around £70. Any advice on: a) does diagnosis sound sensible? b) is changing the sensor in any way a DIY job? I've no idea how to start!! c) how do I make sure I get the right part? Thanks in advance!