fitting new sash windows

[Robbox]

My house has two sash windows on the front, both need replacing.
It's an stone old house and the windows are set into a dressed stone surround.
I have NEVER done something like this before, but I am a practical person with a good eye for details.
My initial feelings were to replace a non-sash window, but I just have problems with the change of the 'look', so I started to look at modern sash windows. The price seems a bit more expensive, so that's why I felt to do a self-fit.
I would imagine that fitting a new sash, made to the same dims as the old ones, should be a simpler operation than fitting a non-sash.
I have read of people using wedges and expanding foam as the initial fix, is this a good way? Do I need further fixing?
These are not big windows, about 1000x1000.
Just how difficult would this be?
Can someone here give a point by point guide?
Finally thanks to all replies.

 

[foxhole]

You can use packers to aid fitting, don't hammer in wedges as you risk distorting the frame, expanding foam gives a strong fixing, you can use frame fixings, but again be aware of distorting the frame when tightening the screws.
When using the foam wet area first.

 

[Robbox]

apart from the actual windows...

what tools, materials etc would you recommend having to hand.

my fear is that I get the old windows out and don't manage to get in the new ones, all in the same day.

For sealing the frame where it meets the stone, is a good silicone frame sealant the best way to go?

How would you rate the difficulty of replacing like for like?

 

[DIYedboy]

I've just fitted a UPVC sash window................for god's sake don't use any foam, these windows are really fussy to fit, the window side frames are very weak, if you distort them the sashes won't slide up n down. I used a firm called quickslide windows, I'd recommend them (they make em and deliver to you!). If you need more help, just ask me

 

[tedridge]

Interesting! I'm looking at replacing wooden sash windows with UPVC one's and am looking at using Quickslide. Are they good quality? They seem much cheaper than other companies which makes one sceptical.

I'm also nervous about having someone else fit them as they are supply only are they?

 

[DIYedboy]

Yes, they are supply only, I think the quality is very good. Fitting could be complicated if you also want to replace the sash boxes too, but this depends on whether they are on the outer or inner leaf, mine were on the inner leaf so I had to replace all that with a 6x2 tanalised frame first. read the installation instructions on the quickslide website (several times)