Per the previous posters, plumbing and electrical must be in normal working order as of possession (assuming you used one of the standard GCAAR purchase contracts). So, if you provide notice of plumbing and electrical issues, the seller is required to make the repairs, even if he hasn't responded.
It's never a good sign when the listing agent doesn't respond one day before settlement. You should make preparations assuming that they haven't made these repairs. If they haven't, then you should have the settlement attorney withhold an escrow so that you can make these repairs after settlement. Here's the way an escrow like this works: You agree to set aside money - assume $500 - from the seller's proceeds that the settlement company holds. Once you make the repairs, you provide receipts to the attorney and are reimbursed. So, if the repairs are $350, the settlement company sends you a check for $350 and the seller will get a check for the balance of $150. But what if the repairs are more than $500? This is the scenario that you want to avoid.
The biggest challenge with an issue like this is to come up with the escrow amount at settlement. Before settlement, you should get quotes to do the work. Even if it's verbal and estimated high, you are in a much better position at settlement to get a higher escrow amount. You'll be in a position of strength if you say that "Ace electrical estimated the electrical repairs could be $700, and Bob's plumbing estimated $500 for the plumbing repairs, so we need to set aside $1,200".
Good luck. Hopefully they've made the repairs and you'll have a smooth closing. Be prepared just in case!