temperature guage

[iowcamper]

a couple of times whilst driving my temp guage has died, once it was off for a couple of mins then picked itself back up, today it did the same but stayed off until after i had stopped the engine and restarted, mentioned it to my mechanic who said probably a faulty sender?? his advice was to buy a new one for 3 or 4 quid and fit it myself, referring to the haynes manual i cant see mention of it and how to replace it anywhere !! off to france in couple of weeks so would like a reliable idea of the temp whilst driving really !
a) does his prognosis sound right
b) where do i get one from - what is their proper title
c) are they easy to replace
d) anything else i should check first

cheers
iowcamper

[ricicles]

put the wires to ground and see if the temp gauge goes to the top, if not it,s a wireing prob.