I doubt there will be a civil war. First of all, retaining Crete - a fiercely republican island- will lead to the appointment of old Liberal party politicians in the government in a far greater extent than OTL. Remember, the Metaxas regime was basically a royal dictatorship where Metaxas was the useful front as he didn't control the army nor he had a party apparatus such as the fascist/nazi dictators. Now if the King wants to survive politically he has to liberalize the government.
Such a government would have both legitimacy (holds Crete and islands as mentioned) and greater appeal in Greece. Moreover the government will have resources be that military, political or financial, to support pro-government groups in mainland Greece. Lastly, the government will control the weapons supply to the various resistance groups. Only after the Italian Armistice ELAS and EDES found themselves with an independent source of weapons (bounty from italian units). As there is no armistice in TTL up to this point, then all the weapon supply is in the hands of the greek government.
In general, the civil war will be butterflied will enormous repercussions for post-war Greece. From a greek point of view with 20/20 hindsight it is worth it having a battleground in Greece if only to avoid the catastrophic civil war.
There is bound to be a pretty severe political crisis within free Greece around 1942-43 over the status of the monarchy. I expect George II will be forced to agree to a referendum before returning from... London right after liberation of the mainland and Sofoulis/Papandreou or Kafanntaris spirited out along with Pangalos from the mainland to head government and army respectively . As for the resistance you are having operation Midas on steroids here and multiple republican resistance groups in OTL destroyed and absorbed by ELAS still around thanks to an earlier start and aid from Crete. The very fact that you remove the republicans from EAM from Grigoriadis and Sarafis downwards will have huge effects on the relative balance of power. And on the relationship between ELAS and the rest on the field.