As Geno said you will need some additional insurance in place before you can do that, i would call your insurer and have them look over your job.
On another note, $15/sq.ft. seems low. You can get around there for a vehicle wrap, and you don't need a 60' lift to install a vehicle wrap. Also, as a 1 man show, what is your timeline on that? It could take you weeks to complete a job that size, and during that time you will be essentially closed to any new opportunities that may come along. It may be more efficient to hire a company that can handle an installation like that, let alone the printing. What type of printer are you using? How many? That is over 5000 square feet of print not taking overlap into consideration, assuming you have 0 mistakes or reprints. How do you verify your overlaps are going to be correct and there isn't any skew.
Nothing is impossible, but not every opportunity is proper to take on alone. Don't be afraid to outsource things above your capabilities, your customer will get what is promised and be happy with you for delivering (in a timely fashion), you can make some money on the markup, you aren't out of commission for weeks, and you can build a relationship with a large national/regional installation company for future projects that are a bit out of reach. Also, you don't have to incur the additional insurance expenses.
Just my opinion, good luck with the bid.
-Cameron