Targus, in both configurations it depends on the users ability to solder. Practically anyone can hold an iron and make a decent splice in single conductor wire without much hassle with a $10 RS iron. That isn't an issue.
The problem with soldering a DBH15 is the closeness of the connecting points and the fact that most people don't buy ultra fine point soldering tips. It gets even worse if you don't have a good temperature adjustable iron.
Based solely on the OP asking if it was possible to buy and HD15 end I can guess he hasn't done allot of soldering. If he had it is a reasonable leap to him knowing they are available and where to get one. With that in mind I gave him an alternate option for going the connection in a way that would be easier for him to accomplish as a beginner. If he isn't a beginner and I guess wrong, no problem he will read my suggestion and ignore it and go in with life.
As for the impedance differences between splicing the cable and attaching directly to the connector they are small and with VGA not as big an issue as you would think. Especially if when you take into account the person making the connections ability, the quality of the cable and the basic limitations of VGA video.
I have made connections of all 3 types, cable splice, junction box and direct soldering, dozens of times and in all cases the was not noticeable video degradation in lengths up to 75'. At the distance he is running short of wrapping the cable around an AC line he should be fine.