Requesting help on PostgreSQL Replication

Hello,

Can I ask you guys for suggestion on my replication
requirements? I'm new to postgresql and the replication itself, so your
inputs will be highly appreciated.

My Situation:

I have deployed a POS unit in our remote store using Openbravo POS
as the software with a local installation of PostgreSQL for database.
Now I will need to connect to this remote database from the central
office to fetch latest data from the store and update products, prices
and customer records. I would need to get the latest data from the
store at least within 4-8hours.

Here are the details about my requirements and info's about the nodes.

Remote Location POS
256mb RAM, 640mhz Celeron CPU, 40gb HDD
Openbravo POS with PostgreSQL (database size aprrox 15mb) on Ubuntu 8.10
Sometimes Erratic, semi congested 384kbps connection shared w/ free wifi access. (If you'll ask why, we don't have a choice for a provider so far.)

Central Server Database Virtual Machine
512mb RAM, 2.2ghz Shared AMD64 X2 CPU, 40gb HDD
Openbravo POS with PostgreSQL on Ubuntu 8.10
Dedicated 1mbps T1 connection

Major Replication Requirements (from the Central
Office side):

1. Apply updates on certain tables like products, customers, users and settings and commit on the remote location POS.
2. Query Sales, Transactions, Inventory and other tables for reporting purposes from POS.
3. Fetch update at least within 4-8 hours interval.
4. Generate Backups

I
know you only provide support in the community for free and I maybe
asking too much, so I'm not expecting a lot. But I would appreciate any
inputs regarding my situation.

Thanks a lot!
cyberjorge