Hi Vikram,
text file upload into HANA is easy - if the files don't contain errors, i.e. you can assign data types to each column and all values in the column are valid for this data type.
The easiest way is to use the upload wizard in HANA Studio: Menu "File" --> Import --> SAP HANA Studio --> Data from local file; this wizard lets you choose excel sheets or csv files.
Other alternatives are placing the csv files on the server and using the "import from" syntax. Here you have to create the target table manually (as an empty table) and also create a .ctl file that gives some parameters to the import. All of that is explained including example in the SQL reference guide at http://help.sap.com/hana/html/sql_import_from.html
As to differences between SLT and SAP Data Services:
Data Services is an ETL tool that can connect to multiple types of data containing systems (more or less any DB; ABAP Dictionary; Hadoop; ...). It can read from and write into these systems, facilitating any type of ETL process between more or less any combination of source and target. It also allows defining complex transformation rules in between, has scheduling capabilities and what have you. In most cases, you don't have any special functionality to generate delta information between two loads from the same source (exceptions apply, e.g. using BW Extractors as sources in DS). That's why DS is mostly operated in batch mode.
SLT on the other hand installs a functionality to get a generic delta on any table - by means of table triggers. This enables the tool to pull data from the source system with a latency of the order of magnitute of one second ("real time"), no batch processing needed here, rather a continuous stream of data from source to target. The primary use case is to replicate from AS ABAP-based systems into SAP HANA, but by now you can also read from non-ABAP sources. Transformation capabilities exist, but are largely limited to DS.
Best,
Richard