Dale,
For the first question, you're scenario sets this up very nicely for the use of multiple subnets. If the company has grown over time, it's like to grow again and likely to need multiple departments too. Creating multiple subnets will help segregate traffic according to your business need (e.g. HR Dept traffic separate from the Marketing Dept). Also for future scalability, if the business continues to grow with one network (such as a 192.168.1.0/24) you'll still need another network. Let's say you pick a 172.16.1.0/24 next. This will work but you'll not be able to take advantage of things like route summarization. Creating a solid logical network scheme will allow for scalability, segmentation and routing efficiency.
For the second question, if it's a point to point connection you could use a fiber optic for the connection:
you're looking at ethernet 1000 Base LX (max of 1804 ft).
Cordially,
Ronnie Wong
Host, ITProTV