Are nail-ins really the "right" way to do replacements?

Replacing 12 windows in the second story of our house near the beach in Orange County, CA. After looking around at a few options, I settled on Milgard Tuscany casement windows, partly for the looks and partly because our neighborhood hardware store is a Milgard dealer and I like to give them business when I can.

My questions as this point are:

1) Retrofit windows seem like a perfectly legitimate option given our mild climate and the relative newness of the house (1990), but one contractor that came out to look at the job said he always prefers to do nail in as that's the right way to do it. The original windows are single pane aluminum with stucco on the back 2/3rds of the house and wood siding on the front 1/3. I like doing things the right way if it's worth it in the long run, but not sure if tearing up all that stucco is worth the hassle. Am I good in sticking with retrofits?

2) Finding a good contractor to install the windows is proving to be tough. The companies suggested by the hardware store happen to be in the middle of big jobs so they aren't available for awhile. Seems like most of the window specialists in the area want to sell me the windows, not just install them. There's also the issue of the difficultly of the job. We have very little space for scaffolding on the sides of our house, so getting to the second story windows isn't going to be easy. Any suggestions for finding a good window installer who can handle something like that and is ok with me buying the windows elsewhere?

Thanks for any info you can provide. Just trying to get things in line before I get started on what is a pretty costly project for my budget.

Here goes:

1. There are quite a few applications that will work well for stucco (stucco flange, pocket set with trim, etc) in the retrofit capacity, however, I think your contractor is correct in that the best and most comprehensive way to do it is by cutting the stucco back and going full nailing flange to the sheathing (pretty sure this is a run on sentence )

2 Most of the really good contractors have relationships (usually born out of historical observations and product vetting) with specific manufacturers. Ladder or pump jacks may be required for the 2nd story access but I haven't yet seen and application that we couldn't reach (although we are having to do some engineering right now for one that is proving to be difficult in Old Town Alexandria).