First, welcome to the group
As a former '01 owner and a current '04 owner, I'll offer my two cents worth:
1) With any used vehicle (MDX no exception) the price vs. the mileage/condition is a major driving force. E.g. for approaximately the same price one can get a low mileage '01 or a high mileage '03. How long you plan on keeping the car should determine your mileage range.
2) All MDXs are quality/desirable cars; however there have been steady improvements every year - with the biggest jump in '03. As you have no doubt read there is an increased risk of transmission problems with an '01/'02.
3) Regarding the Nav, yes I prefer the newer edition; however the '01/'02 Nav was still a fine system. In addition to the obvious Voice Recognition of the newer Nav, it also has much better/broader coverage.
My recommendation is to search for an '03/'04 (you'll stand a much better chance getting a later model certified) - good luck.
PS: I bought both of my MDXs from John Eagle Acura in Houston (ask for Brian Simpson in Internet Sales).
Charter Member Class '01 (Two Time Owner; 2001 & 2004)
'15 Nissan Murano (Gun Metallic / Graphite)
Platinum & Technology, Window Tint, Wheel Locks
'09 Infiniti G37 Coupe (Moonlight White / Stone)
Journey, Premium, Navigation, Tech, Illuminated Kick Plates, Window Tint, Wheel Locks