$1,500,000 - is the total selling price of the farm?
$300,000 - is the amount allocated to personal residence?
Do you have a list that itemizes farm properties? - you need it because not all properties are qualify for 1031...
Do you aware that you need third party accommodator?
Does your client has any similar property in mind for 1031 exchange?
You need completely separate home and business - including land allocation.
If the business part is value $1.400,000 (assuming the selling price allocated to the personal home is $100,000) - that amount should be considered as the price for new property.
100% of the proceeds from the sale of the investment property must be reinvested into a property of like-kind or greater value.
If the cost of the replacement property - let's say $1,000,000 - that means $1.000,000/$1.400,000*100%= 71.42% of the gain would be deferred, and 38,58% of the gain will be taxable.
You need to complete form 8824 - http://www.irs.gov/pub/irs-pdf/f8824.pdf - you would enter all information regarding the exchange and determine if any amounts should be transferred to Schedule D or Form 4797.
section 1031 lists following properties as not qualified - http://www4.law.cornell.edu/uscode/html/uscode26/usc_sec_26_00001031----000-.html
(A) stock in trade or other property held primarily for sale, (B) stocks, bonds, or notes, (C) other securities or evidences of indebtedness or interest, (D) interests in a partnership, (E) certificates of trust or beneficial interests, or (F) choses in action.
In additional you should concern that replacement properties would be "like-kind" - see some discussion here - http://www.us1031.com/qualifiedproperties.htm
I would suggest to start with finding a Qualified Intermediary to facilitate the 1031 Exchange Transaction.