There are a few things to consider. First, you should know that Exchange and Sharepoint servers are not "set and forget" - they need frequent maintenance which means whoever your hire to do this network should have reasonable rates to maintain these servers long term.
The type of server you will need depends on a few factors:How much data will be stored on it
The frequency the users will be hitting it
Will you be hosting applications off it also (i.e. Office)
Will it provide other network services (DHCP, DNS, Activesync, etc)
The question about the *best* routers and switches really depends on what you want to pay. Arguably Cisco equipment is among the best, but do you want to spend several thousand on routers and switches? Maybe Linksys will be fine for you, maybe not. One comment I would make, I advise all my clients to go for Gig-Ethernet as the price has come down so much. The extra speed you get from Gig-E can make a major difference on the LAN.
Finally, for wiring the building make sure to use a reputable contractor. Use CAT-6E cabling throughout - DON'T SKIMP HERE! My most frequent call is replacing shoddy poor quality cabling. You don't want to pay twice for that :-)
~j