Welome to GOY Dont know about rotavators im afraid. Once once its done lots of farm yard manure and well rotted compost into your beds. Happy gardening

Rotavators are NOT the panacea they may seem. You may get an immediate effect of a well tilled garden but all you will do is chop up the perennial weed roots which will then continue to come up all through the season.
No approach is labour free but I would divide your plot into much smaller areas (I use 4 metres by 1 metre which I find about the right size to work or plant on one occasion.) That way it's psychologically far better than being faced with an enormous plot and what looks like endless work.
After rotavating carefully dig over each defined area, removing every bit of large root of couch grass, dandelion, dock etc you can see. However well you do this you will find some still come up later and will need removing.
There is a totally different approach called the deep mulch method which I have used with great success for things like potatoes, but it does assume you have access to a great deal of mulch material. It certainly saves on the labour though and you end up with a very fertile soil.
See http://www.suite101.com/article.cfm/simple_homesteading/60401 though I would say this makes it sound rather easier than the actual practice.
Sorry forgot to say, the best type of rotavator is the really large type with rear tines and tracted wheels. They are less effort to use and dig more deeply than the standard type. You should be able to hire one which will do the original job in a day.

Thanks very much. I will check out the article and give it a go. I will keep telling myself how fab my veg will taste after the effort I put in lol!