On a deal this large, and with little experience, I strongly recommend getting help from a professional if you're serious about making the deal work. A real estate attorney or, at the very least, an experienced real estate agent, will be able to give you specific advice and help you figure this transaction out.
The first mortgage almost certainly has a Due-on-Sale clause. That means that they can technically call the loan if ownership changes. They may call the loan, and they may not, but if you don't have the means of quickly refinancing that loan, it's extremely risky to take ownership and hope they don't call the note. Honestly, they very well may not, and I know people do these deals all the time (If you want to read up on this exact type of deal, it's called a "subject-to"deal because it's subject to existing financing).
As far as your second question goes, it's unlikely you'd need a quitclaim deed unless your friend isn't the actual current owner (if, for instance, he actually has a contract for deed instead of an owner carry). If he is the owner, the lien-holder will jus a need to release the lien once he's repaid.