I'm sure you would, too - considering that the first main dealer who serviced my 370z tried to get away with only replacing one of the air filters (luckily I checked before leaving the premises - I was fuming) - and the second one tried to sell me washer jets at about £70 each, when all they needed was a bit of a cleanout. Generally, main dealers suck. When you give them your own expensive oil to use do they actually put it in, or does someone take it home and sell it on ebay or something? Now that my car is out of warranty I take it to a garage I TRUST (trust is the important word here).
To answer the op's question - a buyer who doesn't know you will have to TRUST you, if you've done the servicing yourself. If I were the buyer I wouldn't trust you, not because you're untrustworthy, but because I don't know you, so either have copious notes & receipts if you do it yourself, or take it to a trustworthy garage/mechanic to get it done & stamped. Whatever you do, don't take it to a main dealer just to get the stamp, unless you have one you trust 100% - they rip you off in every way.
My personal preference would be a trustworthy garage's stamp, every time.