AS400 Query Question

Hello Group,
I'm new to MAPICS and AS400 queries, but do have experience writing SQL 
queries. I've been working on our MAPICS implementation for the last 4 months 
and this is the first time I'm writing AS400 queries. Basically, I'm having 
trouble trying to incorporate GROUP BY aggregate function in an AS400 query. I 
guess I haven't defined my report summary functions and report breaks the right 
way. I would like to query ITEMBL file to get a total on-hand inventory value 
for all warehouses. The SQL version of this would look like this:

SELECT HOUSE, Sum(AVCST* MOHTQ) AS INVENTORY_VALUE
FROM ITEMBL
GROUP BY HOUSE

HOUSE = Warehouse
AVCST = Avg Unit Cost
MOHTQ = On Hand Total Quantity

I would like my report to look like this:

Warehouse       INVENTORY_VALUE
PBC             $107,117.41
PBD             $157,116.41
PBX             $257,116.41

Any suggestions on how to accomplish the above will be appreciated. Could you 
also point me towards good online documentation/books on AS400 queries.

Thanks,
Nandu