Haven't done it with a toddler that young .. DD1 was 2.5yrs when DD2 was born by c/s.
Suggestions ..
Don't lift the 18mth old. It will slow down your recovery, so really try and avoid it to begin with.
Stock up the house well before the birth so you don't need to go out, and get DH to ring you before he heads home, so he can pick up anything you need.
Buy some little step stools, to make it easy for the toddler to climb onto your bed etc.
Cuddles are on the lounge. Sit and let her climb up next to you rather than picking her up for a hug.
Nappy changes on the bed or the lounge. I was actually fine getting done on the floor, so that was an option for me too.
Skip the high chair. Meals are either picnic on the floor (easy sandwich type lunch), or if you have a kiddie table that she can sit at.
Naptime is on your bed, or on a mattress on the floor - do not lift an 18mth into a cot.
Bathing waits until Daddy is home.
TV is your friend. It is not evil, it will not hurt your child

Don't stress over mess .. if the toddler makes a big huge mess, don't worry about it.
A lot depends on the work hours your husband does as well. Is he home in time to cook dinner and bath the toddler? Is he around at breakfast time? How flexible are his hours? If he works for himself, maybe you can work out the time that you do need help and he can arrange to be home? Even a half day in the middle of the week, just to give you a break is good too ... depending on how much planning he needs to get away from work, this could maybe be more of a sponataneous thing, depending on how well you are coping?
But it is doable. Just relax your standards, and take it easy, and it will all work