Valuation help

An entity has a joint ownerhip of an asset with one other party (40%/40%) under a partnership and the remainig 20% was funded through debt. If the entity wants to buy out the ownerhsip % they don’t currently have now and all the existing debt is supposed to retire upon transaction, what should I include in my model to determine the NPV and IRR of the buy out? What I have now is free cash flows from the asset (after the existing debt service) + any adjustment to the cash flow due to the acquisition (expected synergy, cost savings, etc) + Future debt service (based on the amount to borrow to support 50% of the dcf of the asset + pv of their portion of the existing debt to refinance + transaction fees). Does this sound right? Anything else that I missed out or doublecounting? Thanks for your help.