Yes, you can easily do this yourself.
The reason I would consider using an attorney in situations like this relate to the question of what happens if something goes wrong? The attorney is less likely to get things wrong and has insurance to make you whole if they do get it wrong. While costly, your situation may warrant using a patent attorney.
Instructions for paying the issue fee will have arrived with the Notice of Allowance. You can write a check for the correct amount and send it along with the forms that were provided to the PTO.
Applicants and their attorneys or agents are urged to use the Fee(s) Transmittal form >(PTOL-85B) provided with the Notice of Allowance when submitting their payments. Unless >otherwise directed, all post allowance correspondence should be addressed “Mail Stop >Issue Fee.” http://www.uspto.gov/web/offices/pac/mpep/s1306.html
Your indication that you've applied for micro-entity status suggests that you might have a problem if you pay the lower issue fee ($240) and the PTO fails to get your micro-entity status paperwork processed in due course. Attorneys handle this possibility by maintaining a deposit account that the PTO will tap should there by a shortfall in the amount paid. Since you don't have a deposit account, you need to be correct regardless of how well the PTO has managed its other paperwork.
Check the Public Pair database (http://portal.uspto.gov/pair/PublicPair) to see if your paperwork has been received and processed. If so, pay the lower fee. If not, you can wait a bit to see if that status gets changed appropriately and before the deadline to pay. You can call the PTO (examiner or the help line) to see if this can be hurried along or to find out if there is a problem with your paperwork. Another option is to refile the micro entity status petition with your issue fee, but note that this doesn't ensure that you've paid enough and there is no guarantee that your status will be changed before the deadline to file.
If you cannot determine whether micro entity status will be assigned in due time, your safest bet is to pay the small entity fee. Note that if all of this goes south, there is a process for reviving an unintentionally abandoned patent, but that is costly. Note also that while refunds from the PTO are possible, they are not likely and even if you do get one, it will take a long time.
