the 1000 model compared to the 2000 and 3000 has:
1. no microphone (3000 only)
2. is slightly bigger and weighs slightly more
3. has a worse screen
as for modding / hacking
the 1000 is open for pretty much any way of getting a CFW on it
the 2000 has built in a mainboard in later generations that makes it impossbile to put a CFW on it
the 3000 and the latter 2000 versions are not hackable at this point
i guess im gonna link an german(unfortunately) site but w/ a great tutorial on how and what and what not is possible with certain version psp
maby not much of a help...
maybe u should just relay on google translate as its mostly bullet points anyway and not wall´o´texts
http://board.gulli.com/thread/1031543-psp-...en---downgrade/
the red font rite on top says that its actually not possible to hack any PSP w/ a datecode higher than 8C (can find this behin the battery) or the PSP 3000
tho u can temporarily put a CFW on it if the Official Firmware is lower than 5.03
sorry for linking a german page but this has imo the best and most complete collection of how and how not to hack ur PSP
i guess im gonna link this
http://en.wikipedia.org/wiki/PlayStation_Portable as well for clarification on PSP related hardware terms (for example the different mainboard versions)
hope this helps
i for myself would not recommend buying a PSP on ebay
as for getting a CFW on it id recommend getting a PSP 1000 if u not mind paying some extra money
OR
try to find some RL dude that u know or a friend of a friend of urs ... would enable u to actually find out if the certain PSP is CFW capable or at least capable enough for what u wanna do w/ it
OR
find a small store taht is not known for selling loads of PSPs (for example one can still find P!nk edition PSPs [would be model 1000] for a decent price here in germany)
fly safe