New Homeowner / Electric Heat Issues

My husband and I bought our mobile home (65*32 Doublewide) In the deal we said "give us heat and air" and failed to specify what kind..... So we got a Goodman outside a/c unit and electric heat. Our electric bill is running about $650.00 per month. I have called two a/c heat people. They both told me i need to add heat strips because there is only one their. I was told that the blower fan is insufficient which causes only one half of the home to heat and cool. We already already changed to crossover with a brand new 10" flex pipe. We have done the obvious stuff, new weatherstripping around doors, tinting windows. They are double pained windows. How do i find out what kind of heat strips i need? We looked at the interior unit and there is no markers :/ The only thing we can find is 10kh 240 volt. Does it matter who makes them? How do we know what blower fan we can use? Any answer would really help. We were quoted 1000$ to fix this, but if we can get the parts the A/c man said he would have us fixed for a little of nothing cause it would take very long, but the parts were high through his company.