Small business phone system

Please don't be too harsh with me...

My brother is about to purchase a new phone system for his veterinary
practice and has a few bids on NEC IPK Basic systems w & w/o voice
mail. The questions we are having is whether or not we could install a
system ourselves, and which of the systems we've looked at would
provide adequate service for this smallish practice.

I'm fairly well versed at installations of anything technical
(LANetworked computers, regular phone lines, electrical systems, etc.)
as I've been mechanical all my life. I've looked at his existing phone
system and I know I could have installed that, with an instruction
booklet. As a matter of fact, the wiring for that system is done quite
haphazardly above the suspended ceiling.

anyway, I've found the Toshiba DK40i system online that seems to have
adequate capacity, but all this talk about VoIP and endless options has
me a bit confused when looking through his NEC literature and trying to
compare it to what we could purchase online.

Basically, he now has a 4-line (InterTek) rotating system with 6 phones
(including the main reception phone), plus one dedicated line for fax
and another for credit card purchases. He's wanting to have some small
amount of flexibility to add phone lines & phones (we just added a new
office remodel with 4 office stations). He's expecting to have 8 phone
lines and probably 16 phones, which is exactly what the Toshiba system
offers (DK40 10x16). The Toshiba system with (4 hour) Voice Mail, 16
phones {1]20-button 2020SD, [4]10-button 2010SD & [11]10-button 2010H}
including the service unit base and all the cards and a 24-month
warranty is about $2400 online. His NEC bids range from $3200 to $4200
(w/o & w v/m), but all three bids only include 8 phones.

So, what I'm basically trying to find out:

1) is there a major difference in quality or scalabity of either of
these two types of systems, based on the fact that there probably won't
be any more physical expansions in this practice (he might build
somewhere else...)

2)is the difference in the number of actual phones delivered
substantial enough to knock out the NEC bids. I've come to the
conclusion that it is, as long as the actual Toshiba system is a DK40i
(the web site says DK40, and I know there are differences...)

3) what am I missing that is obscured by all the acronym mumbo jumbo of
options and upgrades??

4) being an installation contractor of heating systems for 25 years, do
you think it possible for a do-it-yourselfer to install and manage one
of these types of systems first time out??

I am "relatively" aware of his voice mail needs (about 12-14
employees), auto-attendant features, surge suppression & line
conditioning needs, and uninterruptable power supply requirements
needed for a new installation.

What else haven't I taken into account? He's not on the web (no web
site), but is networked and has business internet service (just got
it...). He currently has no plan to put up a web page, or do fax-back
services, but it'd be nice if he eventually could. I write web pages
for our family, so I'm sure I could get a site up in the next year, if
he needs one.

What am I missing that could make the choice of our doing this job
ourselves (myself) a mistake?? Any "positive advice" givers???

Thanks in advance for any advice offered, and thanks for not pouncing
on me for being so naive when it comes to phone systems.

Joe

.