Dimon, Moldovan minibuses won't impress you )))
What customs are you talking about, Sanya? Just jump on the train and in 3 hours you'll be in Chisinau. Ask Boroda, the organizer, he might have some useful advice based on his experience.
If you have problems with Moldovans, you can try going through Transnistria. If you have problems with Ukrainians, call the border service and sort it out - that's the only way. If there's an expired document or lost documents, there's a chance to resolve it.