Donor piece (green) has rot at the bottom. Looks like one could use just enough to repair that section of the cowl and leave the vent door area alone. (unless there was significant damage elsewhere in removal???)
Where I have the tooling here to fabricate what's needed for the bottom, it would be cheaper for me to make that little bit than to spend the time in sourcing, cost of item, etc. If I had to make the entire part and not just the bottom, then the replacement would be a better choice. Given the limited tools/resources you said you have, unless this is just to dive in and get your feet wet, buying the part would be a better option for you..
