There are several posts on this topic on the Rhodes forum.
We married in Lindos in 2001 in May - it was a wonderful day and very special, so unlike anybody else's wedding that we had been guest at.
We booked with 'another' tour company (not Manos!) and didn't have a particularly good experience - mainly because the 'Wedding Co-ordinator' was very young and very inexperienced. There seemed to be a catalogue of errors right from when we arrived , and the company relieved us of our money and then were not there to help organise, even up to 2 days before our wedding I didn't think it was going to happen, we had 15 family & friends there too so it affected them as well! luckily the staff in our hotel were extremely helpful and supportive and we also knew people in Lindos and Haraki so we were able to plan our reception and get that organised ourselves.
I would suggest visit the island first as you might not find it's for you & might prefer another island? Weddings seem to happen on many of the islands : Santorini, Kos , Skaithos , Kefalonia etc. ....
You will need to have your documents verified at the British Embassy and have them stamped and translated into Greek - the embassy will provided details of authorised translators (then afterwards you will need the marriage certificate translating into English in order to let your bank know etc)
There's lots to do , PM me if you like .