Answers

Flashing is an essential component for any window installation.  This is part of the system which protects from water intrusion and structural deterioration.  There may be gaps between your framing or old frame and replacment window frame.  These are typically filled with insulation (usually foam) for energy conservation and to prevent drafts.

Simplified / general answer above.  As with most construction / improvement details, doing it right depends on products, conditions, and is more complex than a two or three line answer can fully describe.  Your best assurance of having it done right is to engage a responsible and experienced contractor.

It can definitely be repaired, it would need extensive spackling, most likely with 2 part Bondo, then sended primed and painted.

this is something that should not take more than 6-8 hours in total, obviously it does require some skill.

The picture shows the door is stained wood.  The wood is repairable but the door will have to be painted or the repairs will be visible.

Do you know if the estimate from Home Depot was to replace the entire door assembly or just the (door(s)?).   If they estimated the cost including removal and replacement of door jambs, threshold, and door trim, then an alternative that could cost less would be to replace the door slabs only and keep the existing jambs and trim.

Its painted; go to hardware store.  Buy spackle and sand paper.  Sand it down, spacke the scrapes.  Sand the spackle.  Repeat again, though after this spackle prime the door.  Then spackle and prime and paint.  You are looking at spackle 3 or more times, priming it more than once and then paitning two coats.  Alot of work.  But less expensive than a new door.  

Good afternoon,

The picture of the door looks to have polyurethane applied. If this is the case, that’s most likely an oil based finish. If you are trying to apply a latex base interior paint it will not work unless the finish is completely stripped off.

With out physically seeing this myself I can only speculate this to be the issue. The proper tradesmen to contact would be a Painter.

Thank you for inquiring with Ferris Home Improvements but unfortunatley this is not in our scope of work. Feel free to contact us with any questions or future projects. Have a great afternoon