If/then & vlookup with running multiple search criteria

I've received a great deal of help from this forum. It is so very much appreciated!!!
Based upon an item's UPC, I should be able to pull all specific information for the item, including size and color if applicable. Sometimes the UPC has not been entered previously, so I would like to use the Retail Listing Service (RLS) number to locate some of the information. I then use this information (in the Copy and Paste sheet) to copy then paste on to a pdf sticky note to print if necessary.
The data I use comes from the Purge sheet.
I'm not too concerned about populating data in columns D-G, as it's only about 4% of customers that are repeat in special orders.
****Here's what I'm trying to do, and after weeks of reading and looking at tutorials online, cannot figure it out
1. If data is available for column I in the Purge sheet, columns J-S will populate. If there is no information (blank) or "various" to be entered in "Store Fill" column I, when I enter RLS data in column L, I would like information in columns M-S to populate.
For row 151 column N, I have =IF(VLOOKUP($I51,PURGE!$I$2:$S$30000,6,FALSE)=0,"",(VLOOKUP($I51,PURGE!$I$2:$S$30000,6,FALSE)))
What if there is no UPC (I) listed? I can then fill in the Department (J), Quantity Needed (K), and RLS (L). After I put the number in column L, any successive information will populate.
2. I don't use any more than last names for customers, but if columns D (store abbreviation) & E (last name), together, match information in the Purge sheet, F (phone number) & G (email address) will populate.