Makes me wonder if they bought FFC's old machine.
lol
Anyway, yeah, if those problems are what I think they are (95% sure), then they're easy fixes for cheap actually, so you're in luck.
The bass pedal should be using a microswitch with a long bar over the button to help trigger it like the top one in this picture:
http://www.cherrycorp.com/english/sw...s/k_series.jpg. The biggest problem is that when not screwed to the interior plate tight enough, the switch will rotate slightly and the bar will move out of range of the pedal, leaving you with empty kicking. It really takes about 20 minutes of adjusting to get the perfect kick balance once you get it on; too close and you'll only damage the switch or move it again, too far and you'll lose contact. Easy fix on a whole. The other issue with the switch might actually be that the wire contact fell off, which takes about 2 seconds to put back on, though make sure you connect it back to the right terminal.
The hi-hat problem could be a few things and I was never able to exactly pinpoint it when I was working on the same problem on a local machine. At first I thought it might be a static issue where the pad was causing a buildup (aka not grounded right) and was releasing through the piezo trigger, but I was later told that it was possibly an issue with the HH's pad PCB needing a resoldering.
http://channelbeat.com/images/parts/img_27_140.jpg
The part where that cord's plug is connecting to the PCB is apparently where the issue was, however we never had to resolder to fix the issue, I just pushed the socket against the PCB slowly but firmly, then for good measure replaced the piezo sensor (a very inexpensive fix) and checked the cable that attached the HH PCB to the machine for any exposed wiring (there was a little, easily fixed with electrical tape) and the thing worked perfectly afterwards. :P
All in all, if you have access to electrical tape, screwdrivers, piezo triggers, and microswitches, the fixes will cost you.... nothing. If you need triggers or switches, you're gonna be out probably $5 and shipping costs.
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Now, as far as getting it for upgrading, just remember that there is also a hardware switch from V3 to V4. V3 is definitely an awesome mix, but if you can get a good price on it, snag a V5. Like you mentioned, with XG coming out soon (hopefully), finding prices on late mixes will be much easier as arcades liquidate out their old GFdm to acquire new. Don't expect any domestic deals, though. Probably should talk to Zorahk for info on importing stuff, I know he has a reliable seller.
If you haven't played any of the V series yet, I'd say in order of best (IMO) to worst would be V6 (only because of V5's unlocks), V4 (only because of V3's unlocks), V5, V3, V2, V1. As far as non-song differences go:
V1 has an awful song selection GUI.
V2 fixed the above problem, AFAIK.
V3 added Hazard Mode. Last version with Nonstop as well.
V4 added Battle Mode and I think it got rid of Hazard.
V5 brought back Hazard under a new name(?) and added Half Dark (VERY useful mod) and new autoplay options. Also changed the modifier access menu.
V6... did V6 add anything? I forget... :\
Anyway, best of luck on that cab. If you're gonna try to get them to sell, definitely look at things such as: monitor condition (burn-in, nonconvergence, washed out look, whether or not it's a real AC monitor or a TV, etc...) because those are not cheap to replace by any means and they can be very dangerous to tinker with unless you know monitor repair; pad sensitivity (cheap fixes, but you can always argue price based on playability); speaker quality/vibrance; and lights. DM machines can take serious abuse but those are a few things you'll want to look for anyway, obviously. If anything, subpar ratings on any of those can help you save a few bucks when you're haggling.
Keep us updated on the situation.
Odyssey Fun World Tinley Park IL. Drummania 10th mix Questions 
we start the bidding at 10$ 
