If your business will be impacted by having your ONLY computer in the shop, then your disaster plan is woefully inadequate.
"Everyone knows" they need backups of data (although not everyone acts on that need with appropriate urgency) but you also need backup Hardware, and a way to recover after a disaster that takes out both your computer and your data.
Backup Hardware just has to be able to do the most important things eventually. it does not have to be as fast as your primary system. but it has to be close-at-hand, and most businesses end up keeping an old computer on hand for just such purposes. if you have no such older computer available, you may have to buy a new computer and make it the primary, and when that other one comes back off repair, the repaired unit can be the backup.