How do you replace a MT10 Timer on a greenstar 28i boiler?

The MT10 built in timer on my worcester 28i greenstar
boiler refuses to work in timer mode(middle position)
This is the second one Ive had with the same fault.
Contacted worcester who said it will cost £230 to supply and fit.
Believe it is possible to buy the MT10 for £40.
Looked at the instructions but is it possilbe to do yourself, and is boiler cover easy to remove.
Use it in conjunction with a drayton digistat rf601
Is it possible to replace MT10 with a digital one and
will it work with the rf601.

Appreciate any help with this, Many thanks.

Phil
September 2012