I have the presale wallet and password, but went through a number of trials and just now trying to get back on my feet. I have yet to claim my presale and could really use it to help with medical bills. I did not invest much, but every little bit helps for my situation. I've researched, but see conflicting statements about people having issues claiming and no support responses from Ethereum.org. I can say my experience is that I have yet to try and claim it because I have yet to find a confident source to try. I also did try to contact Ethereum.org, but also did not have any response which is not encouraging. Thought I would reach out here to get input. I would be grateful for detailed instructions that also deal with claiming both ETH and ETC as well. Blessings!
Yes, I managed to split my ETC & ETH in 2018. 1st use MEW and make sure to point it to the ETC chain. Then unlock the pre-sale JSON file using MEW which should then show your ETC balance. What I did was to make a transfer to Changelly to convert the ETC into ETH. I created a new ETH wallet to be able to receive the ETH that I will get and did not put it in my pre-sale ETH wallet. That's it. I left my pre-sale ETH where it was and will keep it for a few more years.