If I claim section 179 for a business vehicle a client bought, I can also claim Actual expenses right? Now, is the downside to doing that, is that I can't ever claim standard mileage in future year? My understanding is that if I claim standard mileage during the first year of service, I can switch between standard and actual afterwards? But if I claim actual expense, I can't go back to standard? 

I'm using proseries and I am completing a 1065, and partnership uses 2 vehicles. There are two partners in this business. My understanding is that if a partner uses their personal vehicle and they do not get reimbursed for mileage, they can take a deduction as "unreimbursed Partner Expense." Per proseries, instructions say you can add UPE on supplemental on K-1, but when I transfer that K-1 to the 1040, it gives me an error message saying that it does not know where to put that amount. From the IRS instructions, the UPE goes on line 28 on schedule E, but proseries doesn't allow me to fill out anything on that line. I have to manually override that sections, which creates errors. Please help. 

For those that have done business returns (1065s, 1120s or 1120) how did you learn how to input all the information on proseries? In other words, what resource did you use to learn how to prepare one? Thank you.