You should be able to do it with an update query. You can run your query from design view (hit the view button on toolbar) without actually updating the records while you test your results.
Select what records you want (such as product ids which occur the update table), then based on this fill in the update table and record for those items to update (Price).
As long as it is a one-to-one join and as long as you are not looking to archive old prices, this should be very easy (comparatively). Many Access tuturials in fact use this as an example for update queries.
if the new table gives a wholesale price you can also recalc the retail if it is a set markup (or some formula). This should be easy from an update query, unless your formula to determiine the markup is complex.
if you don't have an access tutorial or manual try a web search on access update queries . .. or search the archives here.