For peace of mind I'd want to change virtually all the details on the account and sign them out remotely otherwise I'd be worried they could take back the account at any time. But changing all these details would almost certainly raise flags on the account.
Does the seller have a history of selling accounts? Do you know them personally or online? Whats the average sale price?
You may be better just buying the stock and selling on your own accounts.
How can I take over his account and get the transactions to come to my PayPal ?
Transactions to your paypal is not a good idea. To get his account, you would need to get both the pair of eb and pp.
It's like buying a business - and best to have PROOF of purchase for eb and pp. You may need notary involvement etc...don't approach a purchase like this with a half-a$$ approach...
need to take over someone's ebay account 
