I dont think the price sounds too bad, do you know the size (Kw rateing) and make of boiler they intend to fit? there are so many different makes and models out there, that you prob could reduce the quote by a fair bit. i only recomend two boilers when doing an install as i have never had any problems with them in the past. remember buy cheap buy twice.
i would also say if the boilers 16yrs old they may have to up size the gas pipe feeding the boiler and any other appliences in the house, as well as changing TRV's ect.
i wouldnt worry too much about the condence too much as its been said before there a pumps to help get rid of that.