adamis220d

hey guys i have a 220d and a couple of months ago my engine managment light came on with check vsc after speaking to lexus they said it is more than likely to be the egr valve due to the problem with carbon build up. luckilly it reset its self and has been fine but i went in to lexus last week just for a part and while there i asked about the problem and they said its a know issue and as a good will for this proble there extending warranty for this problem to 5 years and 124,000 miles mines done 104,000 miles and is 4 and a half years old. they said they would need to stip the engine to so they can put the claim through to give me vertually a new engine and that they havent had one declined but if it was to be declined i would have to pay the labour for striping my engine and putting it back together wich would cost £1400 wich i dont have. my question is really should i trust it and let them do it or just leave it and hope for the best thanks adam