I agree with Windows on Washington. Putting brand new windows in and leaving the old coil and caulk is a little like buying a brand new car and using the tires off the old car. If you don't feel comfortable doing the capping, you can contact a company that does siding and get a price from them. It usually runs somewhere between $50 and $100 per window depending on size and complexity but would be worth it IMO.

Our home was built in 2001. We used Marvin Integrity windows throughout, except for three 12' wide patio sliders. Those are the high end Marvin. I would not buy Marvin windows again. We need to replace those sliders and I'm starting to look around. Friends of ours had a factory built home, called a Wick Home, made by a housing manufacturer in the '70's out of Mazomanie, WI. They had to replace windows and were getting all these very expensive bids because none of their windows were standard sizes. The wife is from Monroe, WI area, where there is an Amish community. They redid their windows with the Amish for a very large savings. She had to go and pick them up and take them home for 3 days, while they did the work but it was about 15,000$ cheaper than the other quotes they were getting. I'm also going to look into that. I haven't been happy with our windows. They get mold and peel paint along the inside casement frame, the big patio doors ice up in the winter along the bottom. The weatherstripping is brittle and breaks off in huge runs. The glass is cold in the winter and I don't think it reflects enough heat in the summer. We had 2 seals break. The Marvin rep came and they covered one, we are working on the other now. But we had to pay for the labor to uninstall the old one and put the new one in. It was at that point they learned that our patio fixed door was assembled backwards. Meaning the outside part of the glass was supposed to be inside. I just think all of this is enough to advise avoiding Marvin.

A sash kit with Dual pane and low-E would have similar performance to a triple pane unit. The STC rating would be better and much less loss of glass over an insert. Installation can be simple to comlex depending on who is installing and the condition of the existing opening . I rarely see them installed correctly by pros unless they are somewhat specialized in these, the ones they got right were because the openings and window needed no modification.

The windows are Pozzi and still in good condition (other than the seals!). I am guessing that the door is Peachtree because that is what the other doors in the house were. Because the door sizes have changed, the price to replace all the glass is way under what a new custom sized door would be. We have replaced all the other doors in the house and had to have custom doors made. We replaced 2 of them because of issues with replacing locks and handles. The other doors were replaced because they were sliders/french doors that were just not holding up well. This door is seldom used in a walk out basement and still works fine.